SQL中update与update select结合语法详解与实例

1、通用update

一般简单的update语法比较通用

语法：

UPDATE table_name
SET column1=value1,
	column2=value2,
	...
WHERE some_column = some_value;

注：若不加where条件则是更新表中的所有数据，
故执行没有where子句的update要慎重再慎重。

实例：

UPDATE subject
SET name='数学',
	type='理学' 
WHERE id = 1;

2、GreenPlum update与select结合

语法：

UPDATE [only] table [[as] alias] 
SET {column = {expression | default} |
	(column [, ...]) = ({expression | default}[, ...])}[, ...]
[FROM fromlist]
[WHERE condition | WHERE current of cursor_name];

注：若不加where条件则是更新表中的所有数据，
故执行没有where子句的update要慎重再慎重。

实例：

UPDATE table1 t1
SET column1 = t2.columnname1
    column2 = t2.columnname2
 FROM (select columnname1,columnname2 from table2) t2
 WHERE t1.column3 = t2.column3
 AND t1.column = '111';

注：对于set列中左边的列不能使用t1.这种别名方式，只能使用column名称

PostgreSQL与GreenPlum语法基本一致

3、MySQL update与select结合

第一种：

语法：

UPDATE table1 SET column1 = (SELECT column FROM table2 [WHERE condition])
WHERE table1.column2 = value;

注：若不加where条件则是更新表中的所有数据，
故执行没有where子句的update要慎重再慎重。

实例：

UPDATE tb_bookcase
SET name = (SELECT bookname FROM tb_bookinfo WHERE tb_bookinfo.type = tb_bookcase.type
		    AND tb_bookinfo.ord_date IN (SELECT MAX(ord_date) FROM tb_bookinfo))
WHERE tb_bookcase.subject = '理学';

第二种：

语法：

UPDATE table1 inner/left/right join table2/(select columns from table3  
 		[inner/left/right join on condition]  [where conditions]) as t3
ON condition
SET column1 = value1,column2 = value2,...
[WHERE conditions]; 

实例：

例1：

UPDATE $table1 a INNER JOIN $table2 b
ON a.user_id = b.user_id 
SET  a.balance = a.balance + b.income,b.status= 1 
WHERE  b.id = 5 AND b.status = 0；

例2：

UPDATE A INNER JOIN 
	(SELECT B.B1 as B1,B.B2 as B2,C.C1 as C1 from B LEFT JOIN C on
	B.B3=C.C3) as t
ON A.A3=t.B1
set A.A1=t.B2,
	A.A2=t.C1;

UPDATE tb_bookcase INNER JOIN 
	(SELECT tb_bookinfo.rid as rid,tb_bookinfo.bookname,department.name LEFT JOIN department on
	tb_bookinfo.depid=department.id) as t
ON tb_bookcase.id=t.rid
set tb_bookcase.bookname=t.bookname,
	tb_bookcase.departname=t.name ;

4、Oracle update与select结合

语法：

UPDATE table1 alias
SET (column_name,column_name ) = (
		SELECT column_name, column_name FROM table2 WHERE table2.column_name = alias.column_name)
[WHERE column_name = VALUE]

注：若不加where条件则是更新表中的所有数据，
故执行没有where子句的update要慎重再慎重。

实例：

例1：

UPDATE t_order t1
SET (ordername,orderprice) = (SELECT detailname,totalprice FROM t_detail WHERE t_detail.detailclasses = t1.classes)
WHERE t1.orderid = 1  

例2：

UPDATE A SET (A1, A2, A3) = (SELECT B1, B2, B3 FROM B WHERE A.ID = B.ID)
WHERE ID IN (SELECT B.ID FROM B WHERE A.ID = B.ID)

5、SQLServer update与select结合

语法：

UPDATE table1 
SET column1 = t2.column1, 
	column1 = t2.column2,
	...  
FROM table1 INNER/LEFT/RIGHT JOIN table2 ON table1.column = table2.column
[WHERE conditions]

注：若不加where条件则是更新表中的所有数据，
故执行没有where子句的update要慎重再慎重。

实例：

UPDATE A
SET A1 = t2.B2 ,
	A2 = t2.C1
FROM A INNER JOIN (
		SELECT  B.B1,B.B2,C.C1 
		FROM B left join C on B.B3 = C.C3) t2 
ON A.A3 = t2.B1
WHERE A.A4 = 1;

UPDATE t_abnormal_fee
SET order_code = t2.order_code ,
	return_fee = t2.express_fee
FROM t_abnormal_fee INNER JOIN (
		SELECT  t_order.id,t_order.order_code,t_detail.express_fee 
		FROM t_order left join t_detail on t_order.name = t_detail.name) t2 
ON t_abnormal_fee.id = t2.id
WHERE t_abnormal_fee.id = 1;