MySQL查询对特定ID的两个不同表中相似列的值求和
假设我们有两个表,并且两个表都有两列PlayerId和PlayerScore。我们需要从这两个表中添加PlayerScore,但仅针对特定的PlayerId。
为此,您可以使用UNION。让我们首先创建一个表-
mysql> create table DemoTable1(PlayerId int,PlayerScore int);
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable1 values(1000,87); mysql> insert into DemoTable1 values(1000,65); mysql> insert into DemoTable1 values(1001,10); mysql> insert into DemoTable1 values(1000,45);
使用select语句显示表中的所有记录-
mysql> select *from DemoTable1;
这将产生以下输出-
+----------+-------------+ | PlayerId | PlayerScore | +----------+-------------+ | 1000 | 87 | | 1000 | 65 | | 1001 | 10 | | 1000 | 45 | +----------+-------------+ 4 rows in set (0.00 sec)
以下是创建第二个表的查询-
mysql> create table DemoTable2(PlayerId int,PlayerScore int);
使用插入命令在表中插入一些记录-
mysql> insert into DemoTable2 values(1000,67); mysql> insert into DemoTable2 values(1001,58); mysql> insert into DemoTable2 values(1000,32);
使用select语句显示表中的所有记录-
mysql> select *from DemoTable2;
这将产生以下输出-
+----------+-------------+ | PlayerId | PlayerScore | +----------+-------------+ | 1000 | 67 | | 1001 | 58 | | 1000 | 32 | +----------+-------------+ 3 rows in set (0.00 sec)
以下是对一个表中的一列与另一表中的列求和的查询。在这里,我们为PlayerId1000添加PlayerScore-
mysql> select sum(firstSum) from (select Sum(PlayerScore) firstSum from DemoTable1 where PlayerId=1000 union select Sum(PlayerScore) firstSum from DemoTable2 where PlayerId=1000) tbl;
这将产生以下输出-
+---------------+ | sum(firstSum) | +---------------+ | 296 | +---------------+ 1 row in set (0.02 sec)