mysql每日一题0723----- 关联查询然后行转列统计_onemorepoint的博客

hope you can enjoy !

CREATE TABLE T0723A
(
ID INT,
机房 VARCHAR(20)
);
CREATE TABLE T0723B 
(
ID INT,
机房ID INT,
主机名称 VARCHAR(20),
主机状态 INT
);
 
INSERT INTO T0723A VALUES (1,'机房A');
INSERT INTO T0723A VALUES (2,'机房B');
INSERT INTO T0723A VALUES (3,'机房C');
 
INSERT INTO T0723B VALUES (1,1,'主机A',1);
INSERT INTO T0723B VALUES (2,1,'主机B',1);
INSERT INTO T0723B VALUES (3,1,'主机C',2);
INSERT INTO T0723B VALUES (4,2,'主机D',0);
INSERT INTO T0723B VALUES (5,2,'主机E',1);CR