当MySQL中的记录为NULL时，在新列中返回0？
为此，您可以使用CASE语句。让我们首先创建一个表-
create table DemoTable703 (Price int);
使用插入命令在表中插入一些记录-
insert into DemoTable703 values(102); insert into DemoTable703 values(null); insert into DemoTable703 values(0); insert into DemoTable703 values(500); insert into DemoTable703 values(100); insert into DemoTable703 values(null); insert into DemoTable703 values(2340);
使用select语句显示表中的所有记录-
select *from DemoTable703;
这将产生以下输出-
+-------+ | Price | +-------+ | 102 | | NULL | | 0 | | 500 | | 100 | | NULL | | 2340 | +-------+ 7 rows in set (0.00 sec)
使用CASE语句-
select Price, case When Price IS NULL Then 0 else Price END AS Result from DemoTable703;
这将产生以下输出-
+-------+--------+ | Price | Result | +-------+--------+ | 102 | 102 | | NULL | 0 | | 0 | 0 | | 500 | 500 | | 100 | 100 | | NULL | 0 | | 2340 | 2340 | +-------+--------+ 7 rows in set (0.00 sec)