Mysql查询语句

mysql查询语句

SELECT column_name,column_name
FROM table_name
[WHERE Clause]
[OFFSET M ][LIMIT N]

1、where条件查询

SELECT field1, field2,...fieldN FROM table_name1, table_name2...
[WHERE condition1 [AND [OR]] condition2.....

2、update修改语句

UPDATE table_name SET field1=new-value1, field2=new-value2
[WHERE Clause]

3、删除表

DELETE FROM table_name [WHERE Clause]

4、like模糊查询，查询包含的字母、字符、汉字等

SELECT field1, field2,...fieldN 
FROM table_name
WHERE field1 LIKE condition1 [AND [OR]] filed2 = '%value'

5、组合、合并查询

SELECT expression1, expression2, ... expression_n
FROM tables
[WHERE conditions]
UNION [ALL | DISTINCT]
SELECT expression1, expression2, ... expression_n
FROM tables
[WHERE conditions];

6、排序查询

SELECT field1, field2,...fieldN table_name1, table_name2...
ORDER BY field1, [field2...] [ASC升序 [DESC降序]]

7、分组查询----分组时可以使用COUNT, SUM, AVG函数

SELECT column_name, function(column_name)
FROM table_name
WHERE column_name operator value
GROUP BY column_name;

8、连接查询

内连接（等值连接）

SELECT a.runoob_id, a.runoob_author, b.runoob_count FROM runoob_tbl a INNER JOIN tcount_tbl b ON a.runoob_author = b.runoob_author; 

这里也可以使用where语句，查询结果相同

SELECT a.runoob_id, a.runoob_author, b.runoob_count FROM runoob_tbl a, tcount_tbl b WHERE a.runoob_author = b.runoob_author; 

左连接：

SELECT a.runoob_id, a.runoob_author, b.runoob_count FROM runoob_tbl a LEFT JOIN tcount_tbl b ON a.runoob_author = b.runoob_author; 

右连接

SELECT a.runoob_id, a.runoob_author, b.runoob_count FROM runoob_tbl a RIGHT JOIN tcount_tbl b ON a.runoob_author = b.runoob_author;