{"id":285,"date":"2021-11-02T09:46:47","date_gmt":"2021-11-02T01:46:47","guid":{"rendered":"http:\/\/47.98.165.52\/?p=285"},"modified":"2021-11-02T09:46:47","modified_gmt":"2021-11-02T01:46:47","slug":"mysql-day01","status":"publish","type":"post","link":"\/?p=285","title":{"rendered":"MySQL DAY01"},"content":{"rendered":"

<hr style=" border:solid; width:100px; height:1px;" color=#000000 size=1"><\/p>\n

MySQL DAY01<\/h2>\n

1.SQL\u3001DB\u3001DBMS\u5206\u522b\u662f\u4ec0\u4e48\uff0c\u4ed6\u4eec\u4e4b\u95f4\u7684\u5173\u7cfb\uff1f<\/h2>\n
DB\uff1a\n        DataBase\uff08\u6570\u636e\u5e93\uff0c\u6570\u636e\u5b9e\u9645\u4e0a\u5728\u786c\u76d8\u4e0a\u4ee5\u6587\u4ef6\u7684\u5f62\u5f0f\u5b58\u5728\uff09\nDBMS\uff1a\n        Database Management System\uff08\u6570\u636e\u5e93\u7ba1\u7406\u7cfb\u7edf\uff0c\u5e38\u89c1\u7684\u6709\uff1aMysql \u3001Oracle \u3001DB2...\uff09\nSQL\uff1a\n        \u7ed3\u6784\u5316\u67e5\u8be2\u8bed\u8a00\uff0c\u662f\u4e00\u95e8\u6807\u51c6\u7684\u8bed\u8a00\u3002\u6807\u51c6\u7684SQL\u9002\u5408\u4e8e\u6240\u4ee5\u7684\u6570\u636e\u5e93\u4ea7\u54c1\u3002\n        SQL\u5c5e\u4e8e\u9ad8\u7ea7\u8bed\u8a00\uff0c\u53ea\u8981\u80fd\u770b\u61c2\u82f1\u8bed\u5355\u8bcd\uff0c\u5199\u51fa\u6765\u7684SQL\u8bed\u53e5\u5c31\u53ef\u4ee5\u8bfb\u61c2\u4ec0\u4e48\u610f\u601d\u3002\n        SQL\u8bed\u53e5\u5728\u6267\u884c\u7684\u65f6\u5019\uff0c\u5b9e\u9645\u4e0a\u5185\u90e8\u4e5f\u4f1a\u5148\u8fdb\u884c\u7f16\u8bd1\uff08\u770b\u4e0d\u89c1\uff0cSQL\u7684\u8bed\u53e5\u7f16\u8bd1\u7531DBMS\u5b8c\u6210\uff09\uff0c\u7136\u540e\u518d\u6267\u884cSQL\u3002\n        \u5173\u7cfb\uff1aDBMSDBMS\u8d1f\u8d23\u6267\u884cSQL\u8bed\u53e5\uff0c\u901a\u8fc7\u6267\u884cSQL\u8bed\u53e5\u6765\u64cd\u4f5cDB\u4e2d\u7684\u6570\u636e  DBMS-\uff08\u6267\u884c\uff09->SQL->DB<\/code><\/pre>\n
2.\u4ec0\u4e48\u662f\u8868\uff1f<\/h2>\n
    \u8868\uff1atable\u662f\u6570\u636e\u5e93\u7684\u57fa\u672c\u7ec4\u6210\u5355\u5143\uff0c\u6240\u6709\u7684\u6570\u636e\u90fd\u4ee5\u8868\u683c\u7684\u5f62\u5f0f\u7ec4\u7ec7\uff0c\u76ee\u7684\u662f\u53ef\u8bfb\u6027\u5f3a\u3002\n    \u4e00\u4e2a\u8868\u5305\u62ec\u884c\u548c\u5217\n        \u884c\uff1a\u88ab\u79f0\u4e3a\u6570\u636e\/\u8bb0\u5f55\uff08data\uff09\n        \u5217\uff1a\u88ab\u79f0\u4e3a\u5b57\u6bb5\uff08column\uff09<\/code><\/pre>\n
\u8868\u7684\u5c5e\u6027\uff1f
\n\u7b54\uff1a\u5b57\u6bb5\u540d\uff0c\u6570\u636e\u7c7b\u578b\u3001\u76f8\u5173\u7684\u7ea6\u675f\u3002<\/p>\n
3.\u5b66\u4e60MySQL\u4e3b\u8981\u8fd8\u662f\u5b66\u4e60SQL\u8bed\u53e5\u3002SQL\u8bed\u53e5\u5305\u62ec\u589e\u5220\u6539\u67e5\uff0cSQL\u8bed\u53e5\u8be5\u5982\u4f55\u5206\u7c7b\uff1f<\/h2>\n
    DQL\uff08\u6570\u636e\u67e5\u8be2\u8bed\u8a00\uff09\uff1a\u67e5\u8be2\u8bed\u53e5\uff0c\u51e1\u662f**select**\u8bed\u53e5\u90fd\u662fDQL\uff1b\n    DML\uff08\u6570\u636e\u64cd\u4f5c\u8bed\u8a00\uff09\uff1a**insert\u3001delete\u3001updata**\uff0c\u5bf9\u8868\u5f53\u4e2d\u7684\u6570\u636e\u8fdb\u884c\u589e\u5220\u6539\uff1b\n    DDL\uff08\u6570\u636e\u5b9a\u4e49\u8bed\u8a00\uff09\uff1acreate\u3001drop\u3001alter \uff0c\u5bf9\u8868\u7ed3\u6784\u7684\u589e\u5220\u6539\uff1b\n    TCL\uff08\u4e8b\u52a1\u63a7\u5236\u8bed\u8a00\uff09\uff1acommit \u63d0\u4ea4\u4e8b\u52a1\uff0crollback\u56de\u6eda\u4e8b\u52a1(TCL\u4e2d\u7684T\u662ftransaction)\uff1b\n    DCL\uff08\u6570\u636e\u63a7\u5236\u8bed\u8a00\uff09\uff1agrant\u6388\u6743\u3001revoke\u64a4\u9500\u6743\u9650\u7b49\u3002<\/code><\/pre>\n
4.\u5bfc\u5165\u6570\u636e<\/h2>\n
**\u7b2c\u4e00\u6b65*\uff1ados\u547d\u4ee4\u7a97\u53e3\uff1a*\n                mysql -uroot -p\n*\u7b2c\u4e8c\u6b65\uff1a\u67e5\u770b\u6709\u54ea\u4e9b\u6570\u636e\u5e93*\n    show databases;(\u8fd9\u4e0d\u662fSQL\u8bed\u53e5\uff0c\u5c5e\u4e8eMysql\u7684\u547d\u4ee4)\n*\u7b2c\u4e09\u6b65\uff1a\u521b\u5efa\u5c5e\u4e8e\u6211\u4eec\u81ea\u5df1\u7684\u6570\u636e\u5e93*\n    create database bjpowernode;(\u8fd9\u4e2a\u4e0d\u662fSQL\u8bed\u53e5\uff0c\u5c5e\u4e8eMySQL\u7684\u547d\u4ee4)\n*\u7b2c\u56db\u6b65\uff1a\u4f7f\u7528bjpowernode\u6570\u636e\u5e93*\n    use bjpowernode;(\u8fd9\u4e2a\u4e0d\u662fSQL\u8bed\u53e5\uff0c\u5c5e\u4e8eMySQL\u7684\u547d\u4ee4)\n*\u7b2c\u4e94\u6b65\uff1a\u67e5\u770b\u5f53\u524d\u4f7f\u7528\u7684\u6570\u636e\u5e93\u4e2d\u6709\u54ea\u4e9b\u8868\uff1f*\nshow tables;\n*\u7b2c\u516d\u6b65\uff1a\u521d\u59cb\u5316\u6570\u636e*\nmysql>source E:\\MySQL\\\u52a8\u529b\u8282\u70b9\uff1aMySQL\u5165\u95e8\u5230\u7cbe\u901a\\\u6570\u636e\u811a\u672c\\bjpowernode.sql\n\u6ce8\u610f\uff1a\u6570\u636e\u521d\u59cb\u5316\u5b8c\u6210\u540e\u6709\u4e09\u5f20\u8868\n\n+-----------------------+\n| Tables_in_bjpowernode |\n+-----------------------+\n| dept                  |\n| emp                   |\n| salgrade              |\n+-----------------------+<\/code><\/pre>\n
5.bjpowernode.sql,\u8fd9\u4e2a\u6587\u4ef6\u4ee5sql\u7ed3\u5c3e\uff0c\u8fd9\u6837\u7684\u6587\u4ef6\u88ab\u79f0\u4e3a\u201csql\u201d\u811a\u672c\u3002\u4ec0\u4e48\u662fsql\u811a\u672c\u5462\uff1f<\/h2>\n
\u7b54\uff1a\u5f53\u4e00\u4e2a\u6587\u4ef6\u7684\u6269\u5c55\u540d\u662f.sql\uff0c\u5e76\u4e14\u8be5\u6587\u4ef6\u4e2d\u7f16\u5199\u4e86\u5927\u91cf\u7684SQL\u8bed\u53e5\u3002\u6211\u4eec\u79f0\u8fd9\u6837\u7684\u6587\u4ef6\u4e3aSQL\u811a\u672c\u3002\nSQL\u811a\u672c\u4e2d\u7684\u6570\u636e\u91cf\u592a\u5927\u7684\u65f6\u5019\u65e0\u6cd5\u6253\u5f00\uff0c\u8bf7\u4f7f\u7528\u641c\u4e8c\u6d4b\u547d\u4ee4\u5b8c\u6210\u521d\u59cb\u5316\u3002<\/code><\/pre>\n
6.\u5220\u9664\u6570\u636e\u5e93\uff1adrop database bjpowernode;<\/h2>\n
7.\u67e5\u770b\u8868\u7684\u7ed3\u6784\uff1a<\/h2>\n
+-----------------------+               \n| Tables_in_bjpowernode |\n+-----------------------+\n| dept                  |           \uff08\u90e8\u95e8\u8868\uff09\n| emp                   |           \uff08\u5458\u5de5\u8868\uff09\n| salgrade              |           \uff08\u5de5\u8d44\u7b49\u7ea7\u8868\uff09\n+-----------------------+\n\nmysql>desc dept;\n+--------+-------------+------+-----+---------+-------+\n| Field  | Type        | Null | Key | Default | Extra |\n+--------+-------------+------+-----+---------+-------+\n| DEPTNO | int         | NO   | PRI | NULL    |       |(\u90e8\u95e8\u7f16\u53f7)\n| DNAME  | varchar(14) | YES  |     | NULL    |       |\uff08\u90e8\u95e8\u540d\u79f0\uff09\n| LOC    | varchar(13) | YES  |     | NULL    |       |\uff08\u90e8\u95e8\u4f4d\u7f6e\uff09\n+--------+-------------+------+-----+---------+-------+\n\nmysql>desc emp;\n+----------+-------------+------+-----+---------+-------+\n| Field    | Type        | Null | Key | Default | Extra |\n+----------+-------------+------+-----+---------+-------+\n| EMPNO    | int         | NO   | PRI | NULL    |       |\uff08\u5458\u5de5\u7f16\u53f7\uff09\n| ENAME    | varchar(10) | YES  |     | NULL    |       |\uff08\u5458\u5de5\u59d3\u540d\uff09\n| JOB      | varchar(9)  | YES  |     | NULL    |       |\uff08\u5de5\u4f5c\u5c97\u4f4d\uff09\n| MGR      | int         | YES  |     | NULL    |       |\uff08\u4e0a\u7ea7\u9886\u5bfc\u7f16\u53f7\uff09\n| HIREDATE | date        | YES  |     | NULL    |       |\uff08\u5165\u804c\u65e5\u671f\uff09\n| SAL      | double(7,2) | YES  |     | NULL    |       |\uff08\u85aa\u8d44\uff09\n| COMM     | double(7,2) | YES  |     | NULL    |       |\uff08\u6d25\u8d34\uff09\n| DEPTNO   | int         | YES  |     | NULL    |       |\uff08\u90e8\u95e8\u7f16\u53f7\uff09\n+----------+-------------+------+-----+---------+-------+\n\nmysql> desc salgrade;\n+-------+------+------+-----+---------+-------+\n| Field | Type | Null | Key | Default | Extra |\n+-------+------+------+-----+---------+-------+\n| GRADE | int  | YES  |     | NULL    |       | (\u7b49\u7ea7)\n| LOSAL | int  | YES  |     | NULL    |       |\uff08\u6700\u4f4e\u85aa\u8d44\uff09\n| HISAL | int  | YES  |     | NULL    |       |\uff08\u6700\u9ad8\u85aa\u8d44\uff09\n+-------+------+------+-----+---------+-------+<\/code><\/pre>\n
8.\u8868\u683c\u4e2d\u7684\u6570\u636e\uff1f<\/h2>\n
mysql> select *\n    -> from emp;\n+-------+--------+-----------+------+------------+---------+---------+--------+\n| EMPNO | ENAME  | JOB       | MGR  | HIREDATE   | SAL     | COMM    | DEPTNO |\n+-------+--------+-----------+------+------------+---------+---------+--------+\n|  7369 | SMITH  | CLERK     | 7902 | 1980-12-17 |  800.00 |    NULL |     20 |\n|  7499 | ALLEN  | SALESMAN  | 7698 | 1981-02-20 | 1600.00 |  300.00 |     30 |\n|  7521 | WARD   | SALESMAN  | 7698 | 1981-02-22 | 1250.00 |  500.00 |     30 |\n|  7566 | JONES  | MANAGER   | 7839 | 1981-04-02 | 2975.00 |    NULL |     20 |\n|  7654 | MARTIN | SALESMAN  | 7698 | 1981-09-28 | 1250.00 | 1400.00 |     30 |\n|  7698 | BLAKE  | MANAGER   | 7839 | 1981-05-01 | 2850.00 |    NULL |     30 |\n|  7782 | CLARK  | MANAGER   | 7839 | 1981-06-09 | 2450.00 |    NULL |     10 |\n|  7788 | SCOTT  | ANALYST   | 7566 | 1987-04-19 | 3000.00 |    NULL |     20 |\n|  7839 | KING   | PRESIDENT | NULL | 1981-11-17 | 5000.00 |    NULL |     10 |\n|  7844 | TURNER | SALESMAN  | 7698 | 1981-09-08 | 1500.00 |    0.00 |     30 |\n|  7876 | ADAMS  | CLERK     | 7788 | 1987-05-23 | 1100.00 |    NULL |     20 |\n|  7900 | JAMES  | CLERK     | 7698 | 1981-12-03 |  950.00 |    NULL |     30 |\n|  7902 | FORD   | ANALYST   | 7566 | 1981-12-03 | 3000.00 |    NULL |     20 |\n|  7934 | MILLER | CLERK     | 7782 | 1982-01-23 | 1300.00 |    NULL |     10 |\n+-------+--------+-----------+------+------------+---------+---------+--------+\n\nmysql> select * from dept;\n+--------+------------+----------+\n| DEPTNO | DNAME      | LOC      |\n+--------+------------+----------+\n|     10 | ACCOUNTING | NEW YORK |\n|     20 | RESEARCH   | DALLAS   |\n|     30 | SALES      | CHICAGO  |\n|     40 | OPERATIONS | BOSTON   |\n+--------+------------+----------+\n\nmysql> select * from salgrade;\n+-------+-------+-------+\n| GRADE | LOSAL | HISAL |\n+-------+-------+-------+\n|     1 |   700 |  1200 |\n|     2 |  1201 |  1400 |\n|     3 |  1401 |  2000 |\n|     4 |  2001 |  3000 |\n|     5 |  3001 |  9999 |\n+-------+-------+-------+<\/code><\/pre>\n
9.\u5e38\u7528\u547d\u4ee4<\/h2>\n
\u67e5\u8be2\u5f53\u524d\u4f7f\u7528\u7684\u6570\u636e\u5e93\uff1aselect database\uff08\uff09\uff1b\n\u67e5\u8be2\u5f53\u524d\u4f7f\u7528\u7684\u6570\u636e\u5e93\u7248\u672c\uff1aselect version\uff08\uff09\uff1b\n\u7ed3\u675f\u4e00\u6761\u8bed\u53e5  \\c \n\u9000\u51famysql    quit<\/code><\/pre>\n
10.\u67e5\u770b\u201c\u6f14\u793a\u6570\u636e\u201d\u7684\u8868\u7ed3\u6784<\/h2>\n
1)\u67e5\u770b\u548c\u6307\u5b9a\u73b0\u6709\u7684\u6570\u636e\u5e93 show databases;\n2)\u6307\u5b9a\u5f53\u524d\u7f3a\u7701\u6570\u636e\u5e93use bjpowernode;\n3)\u67e5\u770b\u5f53\u524d\u5e93\u4e2d\u7684\u8868 show tables;\n4)\u67e5\u770b\u5176\u5b83\u5e93\u4e2d\u7684\u8868 show tables from database_name;\n5)\u67e5\u770b\u8868\u7684\u7ed3\u6784desc table_name;\n6)\u67e5\u770b\u521b\u5efa\u8868\u7684\u8bed\u53e5\uff1ashow create table emp;<\/code><\/pre>\n
11.\u7b80\u5355\u7684\u67e5\u8be2\u8bed\u53e5\uff08DQL\uff09<\/h2>\n
\u8bed\u6cd5\u683c\u5f0f\uff1a\n    select \u5b57\u6bb5\u540d1,\u5b57\u6bb5\u540d2,\u5b57\u6bb5\u540d3,.... from \u8868\u540d;<\/code><\/pre>\n
\u63d0\u793a\uff1a
\n1\u3001\u4efb\u4f55\u4e00\u6761sql\u8bed\u53e5\u4ee5\u201c;\u201d\u7ed3\u5c3e\u3002
\n2\u3001sql\u8bed\u53e5\u4e0d\u533a\u5206\u5927\u5c0f\u5199\u3002<\/p>\n
\u67e5\u8be2\u5458\u5de5\u7684\u5e74\u85aa\uff1f\uff08\u5b57\u6bb5\u53ef\u4ee5\u53c2\u4e0e\u6570\u5b66\u8fd0\u7b97\u3002\uff09<\/p>\n
select ename,sal * 12 from emp;\n    +--------+----------+\n    | ename  | sal * 12 |\n    +--------+----------+\n    | SMITH  |  9600.00 |\n    | ALLEN  | 19200.00 |\n    | WARD   | 15000.00 |\n    | JONES  | 35700.00 |\n    | MARTIN | 15000.00 |\n    | BLAKE  | 34200.00 |\n    | CLARK  | 29400.00 |\n    | SCOTT  | 36000.00 |\n    | KING   | 60000.00 |\n    | TURNER | 18000.00 |\n    | ADAMS  | 13200.00 |\n    | JAMES  | 11400.00 |\n    | FORD   | 36000.00 |\n    | MILLER | 15600.00 |\n    +--------+----------+<\/code><\/pre>\n
\u7ed9\u67e5\u8be2\u7ed3\u6784\u7684\u5217\u91cd\u547d\u540d\uff1a<\/p>\n
select ename\uff0csal*12 as yearsal form emp;<\/code><\/pre>\n
\u522b\u540d\u4e2d\u6709\u4e2d\u6587\uff1f<\/p>\n
select ename,sal * 12 as \u5e74\u85aa from emp; \/\/ \u9519\u8bef\nselect ename,sal * 12 as '\u5e74\u85aa' from emp;\n+--------+----------+\n| ename  | \u5e74\u85aa     |\n+--------+----------+\n| SMITH  |  9600.00 |\n| ALLEN  | 19200.00 |\n| WARD   | 15000.00 |\n| JONES  | 35700.00 |\n| MARTIN | 15000.00 |\n| BLAKE  | 34200.00 |\n| CLARK  | 29400.00 |\n| SCOTT  | 36000.00 |\n| KING   | 60000.00 |\n| TURNER | 18000.00 |\n| ADAMS  | 13200.00 |\n| JAMES  | 11400.00 |\n| FORD   | 36000.00 |\n| MILLER | 15600.00 |\n+--------+----------+<\/code><\/pre>\n
\u6ce8\u610f\uff1a\u6807\u51c6sql\u8bed\u53e5\u4e2d\u8981\u6c42\u5b57\u7b26\u4e32\u4f7f\u7528\u5355\u5f15\u53f7\u62ec\u8d77\u6765\u3002\u867d\u7136mysql\u652f\u6301\u53cc\u5f15\u53f7\uff0c\u5c3d\u91cf\u522b\u7528\u3002<\/p>\n
as\u5173\u952e\u5b57\u53ef\u4ee5\u7701\u7565\uff1f<\/p>\n
    mysql> select empno,ename,sal * 12 yearsal from emp;\n    +-------+--------+----------+\n    | empno | ename  | yearsal  |\n    +-------+--------+----------+\n    |  7369 | SMITH  |  9600.00 |\n    |  7499 | ALLEN  | 19200.00 |\n    |  7521 | WARD   | 15000.00 |\n    |  7566 | JONES  | 35700.00 |\n    |  7654 | MARTIN | 15000.00 |\n    |  7698 | BLAKE  | 34200.00 |\n    |  7782 | CLARK  | 29400.00 |\n    |  7788 | SCOTT  | 36000.00 |\n    |  7839 | KING   | 60000.00 |\n    |  7844 | TURNER | 18000.00 |\n    |  7876 | ADAMS  | 13200.00 |\n    |  7900 | JAMES  | 11400.00 |\n    |  7902 | FORD   | 36000.00 |\n    |  7934 | MILLER | 15600.00 |\n    +-------+--------+----------+<\/code><\/pre>\n
\u67e5\u8be2\u6240\u6709\u5b57\u6bb5\uff1f<\/p>\n
    select * from emp; \/\/ \u5b9e\u9645\u5f00\u53d1\u4e2d\u4e0d\u5efa\u8bae\u4f7f\u7528*\uff0c\u6548\u7387\u8f83\u4f4e\u3002<\/code><\/pre>\n
12.\u6761\u4ef6\u67e5\u8be2<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
\u8fd0\u7b97\u7b26<\/th>\n\u8bf4\u660e<\/th>\n<\/tr>\n<\/thead>\n
=<\/td>\n\u7b49\u4e8e<\/td>\n<\/tr>\n
<>\u6216!=<\/td>\n\u4e0d\u7b49\u4e8e<\/td>\n<\/tr>\n
<<\/td>\n\u5c0f\u4e8e<\/td>\n<\/tr>\n
<=<\/td>\n\u5c0f\u4e8e\u7b49\u4e8e<\/td>\n<\/tr>\n
><\/td>\n\u5927\u4e8e<\/td>\n<\/tr>\n
>=<\/td>\n\u5927\u4e8e\u7b49\u4e8e<\/td>\n<\/tr>\n
between \u2026 and \u2026.<\/td>\n\u4e24\u4e2a\u503c\u4e4b\u95f4,\u7b49\u540c\u4e8e >= and <=<\/td>\n<\/tr>\n
is null<\/td>\n\u4e3anull\uff08is not null \u4e0d\u4e3a\u7a7a\uff09<\/td>\n<\/tr>\n
and<\/td>\n\u5e76\u4e14<\/td>\n<\/tr>\n
or<\/td>\n\u6216\u8005<\/td>\n<\/tr>\n
in<\/td>\n\u5305\u542b\uff0c\u76f8\u5f53\u4e8e\u591a\u4e2aor\uff08not in\u4e0d\u5728\u8fd9\u4e2a\u8303\u56f4\u4e2d\uff09<\/td>\n<\/tr>\n
not    not<\/td>\n\u53ef\u4ee5\u53d6\u975e\uff0c\u4e3b\u8981\u7528\u5728is \u6216in\u4e2d<\/td>\n<\/tr>\n
like<\/td>\nlike\u79f0\u4e3a\u6a21\u7cca\u67e5\u8be2\uff0c\u652f\u6301%\u6216\u4e0b\u5212\u7ebf\u5339\u914d%\u5339\u914d\u4efb\u610f\u4e2a\u5b57\u7b26\u4e0b\u5212\u7ebf\uff0c\u4e00\u4e2a\u4e0b\u5212\u7ebf\u53ea\u5339\u914d\u4e00\u4e2a\u5b57\u7b26<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\u8bed\u6cd5\u683c\u5f0f\uff1a<\/p>\n
    select \n        \u5b57\u6bb5,\u5b57\u6bb5...\n    from\n        \u8868\u540d\n    where\n        \u6761\u4ef6;<\/code><\/pre>\n
\u6267\u884c\u987a\u5e8f\uff1a\u5148from\uff0c\u7136\u540ewhere\uff0c\u6700\u540eselect<\/p>\n
\u67e5\u8be2\u5de5\u8d44\u7b49\u4e8e5000\u7684\u5458\u5de5\u59d3\u540d\uff1f\nselect ename from emp where sal = 5000;\n    +-------+\n    | ename |\n    +-------+\n    | KING  |\n    +-------+\n\u67e5\u8be2SIMITH\u7684\u5de5\u8d44\uff1f\nselect sal from emp where ename = 'SMITH'; \/\/ \u5b57\u7b26\u4e32\u4f7f\u7528\u5355\u5f15\u53f7\u62ec\u8d77\u6765\u3002\n    +--------+\n    | sal    |\n    +--------+\n    | 800.00 |\n    +--------+\n\u627e\u51fa\u5de5\u8d44\u9ad8\u4e8e3000\u7684\u5458\u5de5\uff1f\n    select ename,sal from emp where sal > 3000;\n\n    select ename,sal from emp where sal >= 3000;\n\n    select ename,sal from emp where sal < 3000;\n\n    select ename,sal from emp where sal <= 3000;\n\n\u627e\u51fa\u5de5\u8d44\u4e0d\u7b49\u4e8e3000\u7684\uff1f\n    select ename,sal from emp where sal <> 3000;\n    select ename,sal from emp where sal != 3000;\n\n\u627e\u51fa\u5de5\u8d44\u57281100\u548c3000\u4e4b\u95f4\u7684\u5458\u5de5\uff0c\u5305\u62ec1100\u548c3000\uff1f\n    select ename,sal from emp where sal >= 1100 and sal <= 3000;\n\n    select ename,sal from emp where sal between 1100 and 3000; \/\/ between...and...\u662f\u95ed\u533a\u95f4 [1100 ~ 3000]\n\n    select ename,sal from emp where sal between 3000 and 1100; \/\/ \u67e5\u8be2\u4e0d\u5230\u4efb\u4f55\u6570\u636e\n\nbetween and\u5728\u4f7f\u7528\u7684\u65f6\u5019\u5fc5\u987b\u5de6\u5c0f\u53f3\u5927\u3002\nbetween and\u9664\u4e86\u53ef\u4ee5\u4f7f\u7528\u5728\u6570\u5b57\u65b9\u9762\u4e4b\u5916\uff0c\u8fd8\u53ef\u4ee5\u4f7f\u7528\u5728\u5b57\u7b26\u4e32\u65b9\u9762\u3002\n    select ename from emp where ename between 'A' and 'C';\n    +-------+\n    | ename |\n    +-------+\n    | ALLEN |\n    | BLAKE |\n    | ADAMS |\n    +-------+\n    select ename from emp where ename between 'A' and 'D'; \/\/ \u5de6\u95ed\u53f3\u5f00\u3002\n\n\u627e\u51fa\u54ea\u4e9b\u4eba\u6ca1\u6709\u6d25\u8d34\uff1f\uff08\u5728\u6570\u636e\u5e93\u4e2dNULL\u4e0d\u662f\u4e00\u4e2a\u503c\uff0c\u4ee3\u8868\u4ec0\u4e48\u4e5f\u6ca1\u6709\uff0c\u4e3a\u7a7a\uff09\n\u7a7a\u4e0d\u662f\u4e00\u4e2a\u503c\uff0c\u4e0d\u80fd\u7528\u7b49\u53f7\u8861\u91cf\n\u5fc5\u987b\u4f7f\u7528 is null  \u6216\u8005is not null.\n\nmysql> select ename,sal,comm from emp where comm is null;\n+--------+---------+------+\n| ename  | sal     | comm |\n+--------+---------+------+\n| SMITH  |  800.00 | NULL |\n| JONES  | 2975.00 | NULL |\n| BLAKE  | 2850.00 | NULL |\n| CLARK  | 2450.00 | NULL |\n| SCOTT  | 3000.00 | NULL |\n| KING   | 5000.00 | NULL |\n| ADAMS  | 1100.00 | NULL |\n| JAMES  |  950.00 | NULL |\n| FORD   | 3000.00 | NULL |\n| MILLER | 1300.00 | NULL |\n+--------+---------+------+\n\n\u627e\u51fa\u54ea\u4e9b\u4eba\u6d25\u8d34\u4e0d\u4e3anull\uff1f\nmysql> select ename,sal,comm from emp where comm is not null;\n+--------+---------+---------+\n| ename  | sal     | comm    |\n+--------+---------+---------+\n| ALLEN  | 1600.00 |  300.00 |\n| WARD   | 1250.00 |  500.00 |\n| MARTIN | 1250.00 | 1400.00 |\n| TURNER | 1500.00 |    0.00 |\n+--------+---------+---------+\n\n\u627e\u51fa\u54ea\u4e9b\u4eba\u6ca1\u6709\u6d25\u8d34\uff1f\nmysql> select ename,sal,comm from emp where comm is null or comm=0;\n+--------+---------+------+\n| ename  | sal     | comm |\n+--------+---------+------+\n| SMITH  |  800.00 | NULL |\n| JONES  | 2975.00 | NULL |\n| BLAKE  | 2850.00 | NULL |\n| CLARK  | 2450.00 | NULL |\n| SCOTT  | 3000.00 | NULL |\n| KING   | 5000.00 | NULL |\n| TURNER | 1500.00 | 0.00 |\n| ADAMS  | 1100.00 | NULL |\n| JAMES  |  950.00 | NULL |\n| FORD   | 3000.00 | NULL |\n| MILLER | 1300.00 | NULL |\n+--------+---------+------+\n\n\u627e\u51fa\u5de5\u4f5c\u5c97\u4f4d\u662fMANAGER\u548cSALESMAN\u7684\u5458\u5de5\uff1f\nmysql> select ename,job from emp where job = 'manager' or job = 'salesman';\n+--------+----------+\n| ename  | job      |\n+--------+----------+\n| ALLEN  | SALESMAN |\n| WARD   | SALESMAN |\n| JONES  | MANAGER  |\n| MARTIN | SALESMAN |\n| BLAKE  | MANAGER  |\n| CLARK  | MANAGER  |\n| TURNER | SALESMAN |\n\nand\u548cor\u8054\u5408\u8d77\u6765\u7528\uff1a\u627e\u51fa\u85aa\u8d44\u5927\u4e8e1000\u7684\u5e76\u4e14\u90e8\u95e8\u7f16\u53f7\u662f20\u621630\u90e8\u95e8\u7684\u5458\u5de5\u3002\nselect ename,sal,deptno from emp where sal > 1000 and deptno = 20 or deptno = 30; \/\/ \u9519\u8bef\u7684\nselect ename,sal,deptno from emp where sal > 1000 and (deptno = 20 or deptno = 30); \/\/ \u6b63\u786e\u7684\u3002\n        \u6ce8\u610f\uff1a\u5f53\u8fd0\u7b97\u7b26\u7684\u4f18\u5148\u7ea7\u4e0d\u786e\u5b9a\u7684\u65f6\u5019\u52a0\u5c0f\u62ec\u53f7\u3002\n\nin\u7b49\u540c\u4e8eor\uff1a\u627e\u51fa\u5de5\u4f5c\u5c97\u4f4d\u662fMANAGER\u548cSALESMAN\u7684\u5458\u5de5\uff1f\nselect ename,job from emp where job = 'SALESMAN' or job = 'MANAGER';\nselect ename,job from emp where job in('SALESMAN', 'MANAGER');\n\nselect ename,job from emp where sal in(800, 5000); \/\/ in\u540e\u9762\u7684\u503c\u4e0d\u662f\u533a\u95f4\uff0c\u662f\u5177\u4f53\u7684\u503c\u3002\n+-------+-----------+\n| ename | job       |\n+-------+-----------+\n| SMITH | CLERK     |\n| KING  | PRESIDENT |\n+-------+-----------+\n\nnot in: \u4e0d\u5728\u8fd9\u51e0\u4e2a\u503c\u5f53\u4e2d\u3002\nselect ename,job from emp where sal not in(800, 5000);\n\n\u6a21\u7cca\u67e5\u8be2like?\n\u627e\u51fa\u540d\u5b57\u5f53\u4e2d\u542b\u6709O\u7684\uff08\u5728\u6a21\u7cca\u67e5\u8be2\u4e2d\uff0c\u5fc5\u987b\u638c\u63e1\u4e24\u4e2a\u7b26\u53f7\uff1a%\u4ee3\u8868\u591a\u4e2a\u5b57\u7b26\uff0c_\u4ee3\u8868\u4efb\u610f\u4e00\u4e2a\u5b57\u7b26\uff09\uff1f\nmysql> select ename from emp where ename like '%o%';\n+-------+\n| ename |\n+-------+\n| JONES |\n| SCOTT |\n| FORD  |\n+-------+\n\n\u627e\u51fa\u540d\u5b57\u4e2d\u7b2c\u4e8c\u4e2a\u5b57\u6bcd\u662fA\u7684\uff1f\nmysql> select ename from emp where ename like '_a%';\n+--------+\n| ename  |\n+--------+\n| WARD   |\n| MARTIN |\n| JAMES  |\n\n\u627e\u51fa\u540d\u5b57\u4e2d\u6709\u4e0b\u5212\u7ebf\u7684\uff1f\nselect name from t_user where name like '%\\_%';\n+---------+\n| name    |\n+---------+\n| WANG_WU |\n+---------+<\/code><\/pre>\n
13.\u6392\u5e8f\uff08\u5347\u5e8f\u3001\u964d\u5e8f\uff09<\/h2>\n
\u6309\u7167\u5de5\u8d44\u5347\u5e8f\uff0c\u627e\u51fa\u5458\u5de5\u540d\u548c\u85aa\u8d44\uff1f\nselect \n    ename,sal \nfrom \n    emp \norder by\n    sal;\n\n+--------+---------+\n| ename  | sal     |\n+--------+---------+\n| SMITH  |  800.00 |\n| JAMES  |  950.00 |\n| ADAMS  | 1100.00 |\n| WARD   | 1250.00 |\n| MARTIN | 1250.00 |\n| MILLER | 1300.00 |\n| TURNER | 1500.00 |\n| ALLEN  | 1600.00 |\n| CLARK  | 2450.00 |\n| BLAKE  | 2850.00 |\n| JONES  | 2975.00 |\n| SCOTT  | 3000.00 |\n| FORD   | 3000.00 |\n| KING   | 5000.00 |\n+--------+---------+<\/code><\/pre>\n
\u6ce8\u610f\uff1a\u9ed8\u8ba4\u662f\u5347\u5e8f\u3002\u600e\u4e48\u6307\u5b9a\u5347\u5e8f\u6216\u8005\u964d\u5e8f\u5462\uff1fasc\u8868\u793a\u5347\u5e8f\uff0cdesc\u8868\u793a\u964d\u5e8f\u3002<\/p>\n
    select ename , sal from emp order by sal; \/\/ \u5347\u5e8f\n    select ename , sal from emp order by sal asc; \/\/ \u5347\u5e8f\n    select ename , sal from emp order by sal desc; \/\/ \u964d\u5e8f\u3002\n\n\u6309\u7167\u5de5\u8d44\u7684\u964d\u5e8f\u6392\u5217\uff0c\u5f53\u5de5\u8d44\u76f8\u540c\u7684\u65f6\u5019\u518d\u6309\u7167\u540d\u5b57\u7684\u5347\u5e8f\u6392\u5217\u3002\n    select ename,sal from emp order by sal desc;\n    select ename,sal from emp order by sal desc , ename asc;<\/code><\/pre>\n
\u6ce8\u610f\uff1a\u8d8a\u9760\u524d\u7684\u5b57\u6bb5\u8d8a\u80fd\u8d77\u5230\u4e3b\u5bfc\u4f5c\u7528\u3002\u53ea\u6709\u5f53\u524d\u9762\u7684\u5b57\u6bb5\u65e0\u6cd5\u5b8c\u6210\u6392\u5e8f\u7684\u65f6\u5019\uff0c\u624d\u4f1a\u542f\u7528\u540e\u9762\u7684\u5b57\u6bb5\u3002<\/p>\n
\u627e\u51fa\u5de5\u4f5c\u5c97\u4f4d\u662fSALESMAN\u7684\u5458\u5de5\uff0c\u5e76\u4e14\u8981\u6c42\u6309\u7167\u85aa\u8d44\u7684\u964d\u5e8f\u6392\u5217\u3002\nmysql> select ename,sal from emp where job='SALESMAN' order by sal desc;\n+--------+---------+\n| ename  | sal     |\n+--------+---------+\n| ALLEN  | 1600.00 |\n| TURNER | 1500.00 |\n| WARD   | 1250.00 |\n| MARTIN | 1250.00 |\n+--------+---------+<\/code><\/pre>\n
select   \u5b57\u6bb5                     3<\/p>\n
from\u8868\u540d                      1<\/p>\n
where\u6761\u4ef6                     2<\/p>\n
order by...                     4
\n.
\n*order by\u662f\u6700\u540e\u6267\u884c\u7684\u3002<\/p>\n
14.\u5206\u7ec4\u51fd\u6570\uff08\u4e00\u5171\u4e94\u4e2a\uff09\uff1f<\/h2>\n
count \u8ba1\u6570
\nsum \u6c42\u548c
\navg \u5e73\u5747\u503c
\nmax \u6700\u5927\u503c
\nmin \u6700\u5c0f\u503c<\/p>\n
\u8bb0\u4f4f\uff1a\u6240\u6709\u7684\u5206\u7ec4\u51fd\u6570\u90fd\u662f\u5bf9\u201c\u67d0\u4e00\u7ec4\u201d\u6570\u636e\u8fdb\u884c\u64cd\u4f5c\u7684\u3002<\/strong><\/p>\n
\u627e\u51fa\u5de5\u8d44\u603b\u548c\uff1f\nselect sum(sal) from emp;\n\u627e\u51fa\u6700\u9ad8\u5de5\u8d44\uff1f\nselect max(sal) from emp;\n\u627e\u51fa\u6700\u4f4e\u5de5\u8d44\uff1f\nselect min(sal) from emp;\n\u627e\u51fa\u5e73\u5747\u5de5\u8d44\uff1f\nselect avg(sal) from emp;\n\u627e\u51fa\u603b\u4eba\u6570\uff1f\nselect count(*) from emp;\nselect count(ename) from emp\uff1b<\/code><\/pre>\n
\u5206\u7ec4\u51fd\u6570\u4e00\u51715\u4e2a\u3002
\n\u5206\u7ec4\u51fd\u6570\u8fd8\u6709\u53e6\u4e00\u4e2a\u540d\u5b57\uff1a\u591a\u884c\u5904\u7406\u51fd\u6570\u3002
\n\u591a\u884c\u5904\u7406\u51fd\u6570\u7684\u7279\u70b9\uff1a\u8f93\u5165\u591a\u884c\uff0c\u6700\u7ec8\u8f93\u51fa\u7684\u7ed3\u679c\u662f1\u884c\u3002<\/p>\n
\u5206\u7ec4\u51fd\u6570\u81ea\u52a8\u5ffd\u7565NULL\u3002<\/strong><\/p>\n
select count(comm) from emp;\n+-------------+\n| count(comm) |\n+-------------+\n|           4 |\n+-------------+\n\nselect sum(comm) from emp;\n+-----------+\n| sum(comm) |\n+-----------+\n|   2200.00 |\n+-----------+\n\nselect sum(comm) from emp where comm is not null; \/\/ \u4e0d\u9700\u8981\u989d\u5916\u6dfb\u52a0\u8fd9\u4e2a\u8fc7\u6ee4\u6761\u4ef6\u3002sum\u51fd\u6570\u81ea\u52a8\u5ffd\u7565NULL\u3002\n\n\u627e\u51fa\u5de5\u8d44\u9ad8\u4e8e\u5e73\u5747\u5de5\u8d44\u7684\u5458\u5de5\uff1f\nmysql> select ename,sal from emp where sal>avg(sal);\nERROR 1111 (HY000): Invalid use of group function<\/code><\/pre>\n
\u601d\u8003\u9519\u8bef\u539f\u56e0\uff1f
\nSQL\u8bed\u53e5\u5f53\u4e2d\u6709\u4e00\u6761\u8bed\u6cd5\u6cd5\u5219\uff0c\u5206\u7ec4\u51fd\u6570\u4e0d\u53ef\u76f4\u63a5\u4f7f\u7528\u5728where\u5b50\u53e5\u5f53\u4e2d\u3002why?
\n\u7b54\uff1a\u56e0\u4e3agroup by \u662f\u5728where \u6267\u884c\u4e4b\u540e\u624d\u4f1a\u6267\u884c\u7684\u3002<\/p>\n
\u6b63\u89e3\uff1a<\/strong><\/p>\n
\u7b2c\u4e00\u6b65\uff1a\u627e\u51fa\u5e73\u5747\u5de5\u8d44\n        select avg(sal) from emp;\n        +-------------+\n        | avg(sal)    |\n        +-------------+\n        | 2073.214286 |\n        +-------------+\n\u7b2c\u4e8c\u6b65\uff1a\u627e\u51fa\u9ad8\u4e8e\u5e73\u5747\u5de5\u8d44\u7684\u5458\u5de5\n        select ename,sal from emp where sal > 2073.214286;\n        +-------+---------+\n        | ename | sal     |\n        +-------+---------+\n        | JONES | 2975.00 |\n        | BLAKE | 2850.00 |\n        | CLARK | 2450.00 |\n        | SCOTT | 3000.00 |\n        | KING  | 5000.00 |\n        | FORD  | 3000.00 |\n        +-------+---------+\n\n\u5408\u5e76\u5b50\u67e5\u8be2\uff1aselect ename,sal from emp where sal > (select avg(sal) from emp);<\/code><\/pre>\n
count()\u548ccount\uff08comm\uff09\u7684\u533a\u522b\uff1f
\n\u7b54\uff1acount(<\/em>):\u4e0d\u662f\u7edf\u8ba1\u67d0\u4e2a\u5b57\u6bb5\u4e2d\u6570\u636e\u7684\u4e2a\u6570\uff0c\u800c\u662f\u7edf\u8ba1\u603b\u8bb0\u5f55\u6761\u6570\u3002\uff08\u548c\u67d0\u4e2a\u5b57\u6bb5\u65e0\u5173\uff09
\ncount(comm): \u8868\u793a\u7edf\u8ba1comm\u5b57\u6bb5\u4e2d\u4e0d\u4e3aNULL\u7684\u6570\u636e\u603b\u6570\u91cf\u3002<\/strong><\/p>\n
\u5206\u7ec4\u51fd\u6570\u4e5f\u80fd\u7ec4\u5408\u8d77\u6765\u7528\uff1a<\/p>\n
select count(*),sum(sal),avg(sal),max(sal),min(sal) from emp;\n\n    +----------+----------+-------------+----------+----------+\n    | count(*) | sum(sal) | avg(sal)    | max(sal) | min(sal) |\n    +----------+----------+-------------+----------+----------+\n    |       14 | 29025.00 | 2073.214286 |  5000.00 |   800.00 |\n    +----------+----------+-------------+----------+----------+<\/code><\/pre>\n
15\u3001\u5355\u884c\u5904\u7406\u51fd\u6570<\/h2>\n
\u4ec0\u4e48\u662f\u5355\u884c\u5904\u7406\u51fd\u6570\uff1f\n    \u8f93\u5165\u4e00\u884c\uff0c\u8f93\u51fa\u4e00\u884c\u3002\n\n\u8ba1\u7b97\u6bcf\u4e2a\u5458\u5de5\u7684\u5e74\u85aa\uff1f\n    select ename,(sal+comm)*12 as yearsal from emp;<\/code><\/pre>\n
\u91cd\u70b9\uff1a\u6240\u6709\u6570\u636e\u5e93\u90fd\u662f\u8fd9\u6837\u89c4\u5b9a\u7684\uff0c\u53ea\u8981\u6709NULL\u53c2\u4e0e\u7684\u8fd0\u7b97\u7ed3\u679c\u4e00\u5b9a\u662fNULL\u3002<\/p>\n
\u4f7f\u7528ifnull\u51fd\u6570\uff1a\nselect ename,(sal+ifnull(comm,0))*12 as yearsal from emp;<\/code><\/pre>\n
ifnull() \u7a7a\u5904\u7406\u51fd\u6570\uff1f
\nifnull(\u53ef\u80fd\u4e3aNULL\u7684\u6570\u636e,\u88ab\u5f53\u505a\u4ec0\u4e48\u5904\u7406) \uff1a \u5c5e\u4e8e\u5355\u884c\u5904\u7406\u51fd\u6570\u3002<\/p>\n
select ename,ifnull(comm,0) as comm from emp;\n+--------+---------+\n| ename  | comm    |\n+--------+---------+\n| SMITH  |    0.00 |\n| ALLEN  |  300.00 |\n| WARD   |  500.00 |\n| JONES  |    0.00 |\n| MARTIN | 1400.00 |\n| BLAKE  |    0.00 |\n| CLARK  |    0.00 |\n| SCOTT  |    0.00 |\n| KING   |    0.00 |\n| TURNER |    0.00 |\n| ADAMS  |    0.00 |\n| JAMES  |    0.00 |\n| FORD   |    0.00 |\n| MILLER |    0.00 |\n+--------+---------+<\/code><\/pre>\n
16.group by \u548c having<\/h2>\n
group by:\u6309\u7167\u67d0\u4e2a\u5b57\u6bb5\u6216\u8005\u67d0\u4e9b\u5b57\u6bb5\u8fdb\u884c\u5206\u7ec4\u3002
\nhaving\uff1a\u5bf9\u5206\u7ec4\u4e4b\u540e\u7684\u6570\u636e\u8fdb\u884c\u518d\u6b21\u8fc7\u6ee4\u3002
\nhaving\u5fc5\u987b\u548cgroup by\u4e00\u8d77\u4f7f\u7528
\n\u6848\u4f8b\uff1a\u627e\u51fa\u6bcf\u4e2a\u5de5\u4f5c\u5c97\u4f4d\u7684\u6700\u9ad8\u85aa\u8d44<\/p>\n
select xx from emp group by job;\nmysql> select job,max(sal) from emp group by job;\n+-----------+----------+\n| job       | max(sal) |\n+-----------+----------+\n| CLERK     |  1300.00 |\n| SALESMAN  |  1600.00 |\n| MANAGER   |  2975.00 |\n| ANALYST   |  3000.00 |\n| PRESIDENT |  5000.00 |\n+-----------+----------+<\/code><\/pre>\n
..<\/p>\n
select ename,max(sal),job from emp group by job;<\/code><\/pre>\n
\u4ee5\u4e0a\u5728mysql\u5f53\u4e2d\uff0c\u67e5\u8be2\u7ed3\u679c\u662f\u6709\u7684\uff0c\u4f46\u662f\u7ed3\u679c\u6ca1\u6709\u610f\u4e49\uff0c\u5728Oracle\u6570\u636e\u5e93\u5f53\u4e2d\u4f1a\u62a5\u9519\u3002\u8bed\u6cd5\u9519\u8bef\u3002
\nOracle\u7684\u8bed\u6cd5\u89c4\u5219\u6bd4MySQL\u8bed\u6cd5\u89c4\u5219\u4e25\u8c28\u3002
\n\u8bb0\u4f4f\u4e00\u4e2a\u89c4\u5219\uff1a\u5f53\u4e00\u6761\u8bed\u53e5\u4e2d\u6709group by\u7684\u8bdd\uff0cselect\u540e\u9762\u53ea\u80fd\u8ddf\u5206\u7ec4\u51fd\u6570\u548c\u53c2\u4e0e\u5206\u7ec4\u7684\u5b57\u6bb5\u3002<\/p>\n
\u6ce8\u610f\uff1a\u5206\u7ec4\u51fd\u6570\u4e00\u822c\u90fd\u4f1a\u548cgroup by\u8054\u5408\u4f7f\u7528\uff0c\u8fd9\u4e5f\u662f\u4e3a\u4ec0\u4e48\u5b83\u88ab\u79f0\u4e3a\u5206\u7ec4\u51fd\u6570\u7684\u539f\u56e0\u3002<\/strong>
\n\u5e76\u4e14\u4efb\u4f55\u4e00\u4e2a\u5206\u7ec4\u51fd\u6570\uff08count sum avg max min\uff09\u90fd\u662f\u5728group by\u8bed\u53e5\u6267\u884c\u7ed3\u675f\u4e4b\u540e\u624d\u4f1a\u6267\u884c\u7684\u3002
\n\u5f53\u4e00\u6761sql\u8bed\u53e5\u6ca1\u6709group by\u7684\u8bdd\uff0c\u6574\u5f20\u8868\u7684\u6570\u636e\u4f1a\u81ea\u6210\u4e00\u7ec4\u3002
\n----------------------------------
\n\u591a\u4e2a\u5b57\u6bb5\u80fd\u4e0d\u80fd\u8054\u5408\u8d77\u6765\u4e00\u5757\u5206\u7ec4\uff1f<\/p>\n
\u6848\u4f8b\uff1a\u627e\u51fa\u6bcf\u4e2a\u90e8\u95e8\u4e0d\u540c\u5de5\u4f5c\u5c97\u4f4d\u7684\u6700\u9ad8\u85aa\u8d44\u3002\nselect \n    deptno,job,max(sal)\nfrom\n    emp\ngroup by\n    deptno,job;\n+--------+-----------+----------+\n| deptno | job       | max(sal) |\n+--------+-----------+----------+\n|     20 | CLERK     |  1100.00 |\n|     30 | SALESMAN  |  1600.00 |\n|     20 | MANAGER   |  2975.00 |\n|     30 | MANAGER   |  2850.00 |\n|     10 | MANAGER   |  2450.00 |\n|     20 | ANALYST   |  3000.00 |\n|     10 | PRESIDENT |  5000.00 |\n|     30 | CLERK     |   950.00 |\n|     10 | CLERK     |  1300.00 |\n+--------+-----------+----------+\n\n\u6848\u4f8b\uff1a\u627e\u51fa\u6bcf\u4e2a\u90e8\u95e8\u7684\u6700\u9ad8\u85aa\u8d44\uff0c\u8981\u6c42\u663e\u793a\u85aa\u8d44\u5927\u4e8e2900\u7684\u6570\u636e\u3002\n\n    \u7b2c\u4e00\u6b65\uff1a\u627e\u51fa\u6bcf\u4e2a\u90e8\u95e8\u7684\u6700\u9ad8\u85aa\u8d44\n    select max(sal),deptno from emp group by deptno;\n    +----------+--------+\n    | max(sal) | deptno |\n    +----------+--------+\n    |  5000.00 |     10 |\n    |  3000.00 |     20 |\n    |  2850.00 |     30 |\n    +----------+--------+\n\n    \u7b2c\u4e8c\u6b65\uff1a\u627e\u51fa\u85aa\u8d44\u5927\u4e8e2900\n    select max(sal),deptno from emp group by deptno having max(sal) > 2900; \/\/ \u8fd9\u79cd\u65b9\u5f0f\u6548\u7387\u4f4e\u3002\n    +----------+--------+\n    | max(sal) | deptno |\n    +----------+--------+\n    |  5000.00 |     10 |\n    |  3000.00 |     20 |\n    +----------+--------+\n\n    select max(sal),deptno from emp where sal > 2900 group by deptno;  \/\/ \u6548\u7387\u8f83\u9ad8\uff0c\u5efa\u8bae\u80fd\u591f\u4f7f\u7528where\u8fc7\u6ee4\u7684\u5c3d\u91cf\u4f7f\u7528where\u3002\n    +----------+--------+\n    | max(sal) | deptno |\n    +----------+--------+\n    |  5000.00 |     10 |\n    |  3000.00 |     20 |\n    +----------+--------+\n\n\u627e\u51fa\u6bcf\u4e2a\u90e8\u95e8\u7684\u5e73\u5747\u85aa\u8d44\uff0c\u8981\u6c42\u663e\u793a\u85aa\u8d44\u5927\u4e8e2000\u7684\u6570\u636e\u3002\n\u7b2c\u4e00\u6b65\uff1a\u627e\u51fa\u6bcf\u4e2a\u90e8\u95e8\u7684\u5e73\u5747\u85aa\u8d44\nselect deptno,avg(sal) from emp group by    deptno;\n+--------+-------------+\n| deptno | avg(sal)    |\n+--------+-------------+\n|     10 | 2916.666667 |\n|     20 | 2175.000000 |\n|     30 | 1566.666667 |\n+--------+-------------+\n\n\u7b2c\u4e8c\u6b65\uff1a\u8981\u6c42\u663e\u793a\u85aa\u8d44\u5927\u4e8e2000\u7684\u6570\u636e\nselect deptno,avg(sal) from emp group by deptno having avg(sal) > 2000; \n+--------+-------------+\n| deptno | avg(sal)    |\n+--------+-------------+\n|     10 | 2916.666667 |\n|     20 | 2175.000000 |\n+--------+-------------+\n\nwhere\u540e\u9762\u4e0d\u80fd\u4f7f\u7528\u5206\u7ec4\u51fd\u6570\uff1a\n    select deptno,avg(sal) from emp where avg(sal) > 2000 group by deptno;  \/\/ \u9519\u8bef\u4e86\u3002\n    \u8fd9\u79cd\u60c5\u51b5\u53ea\u80fd\u4f7f\u7528having\u8fc7\u6ee4\u3002<\/code><\/pre>\n
17.\u603b\u7ed3\u4e00\u4e2a\u5b8c\u6574\u7684DQL\u8bed\u53e5\u600e\u4e48\u5199\uff1f<\/h2>\n
select              5\n    ...\nfrom                    1\n    ...\nwhere               2\n    ...\ngroup by            3\n    ...\nhaving              4\n    ...\norder by            6\n    ...<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"
<hr style=" border:solid; width:100px; height:1px;" col   \u2026 …<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0},"categories":[23],"tags":[24],"_links":{"self":[{"href":"\/index.php?rest_route=\/wp\/v2\/posts\/285"}],"collection":[{"href":"\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=285"}],"version-history":[{"count":1,"href":"\/index.php?rest_route=\/wp\/v2\/posts\/285\/revisions"}],"predecessor-version":[{"id":286,"href":"\/index.php?rest_route=\/wp\/v2\/posts\/285\/revisions\/286"}],"wp:attachment":[{"href":"\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=285"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=285"},{"taxonomy":"post_tag","embeddable":true,"href":"\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=285"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}