标签:salary name UNION scholor union student SQL test id
SQL语句UNION和union all的用法
主要说UNION ALL
功能:
将两个流式数据合并
注意:
两个流式数据的字段必须完全一致,包括字段类型和字段顺序。
union和union all的异同点
UNION ALL允许重复值,UNION不允许重复值。
在实时计算Flink版系统中,UNION相当于UNION ALL+Distinct,运行效率低,通常不推荐使用UNION。
测试数据
1.创建示例表(SQLSERVER)
创建test_u1
CREATE TABLE test_u1(
--主键自增:identity(起始值,增量)
id int identity (1,1) primary key
,name nvarchar(100) null
,student_id nvarchar(100) null
,scholor nvarchar(100) null
,salary int
)
insert into test_u1(name,student_id,scholor,salary) values('boyunv01','20211113','primary','100');
insert into test_u1(name,student_id,scholor,salary) values('boyunv02','20211114','junior','200');
--insert into test_u1(name,student_id,scholor,salary) values('boyunv03','20211115','senior','500');
--insert into test_u1(name,student_id,scholor,salary) values('boyunv04','20211116','college','9000');
--insert into test_u1(name,student_id,scholor,salary) values('boyunv05','20211117','master','30000');
--insert into test_u1(name,student_id,scholor,salary) values('boyunv06','20211118','doctor','60000');
select * from test_u1
创建test_u2和insert语句
CREATE TABLE test_u2(
--主键自增:identity(起始值,增量)
id int identity (1,1) primary key
,name nvarchar(100) null
,student_id nvarchar(100) null
,scholor nvarchar(100) null
,salary int
)
insert into test_u2(name,student_id,scholor,salary) values('boyunv01','20211113','primary','100');
insert into test_u2(name,student_id,scholor,salary) values('boyunv02','20211114','junior','200');
insert into test_u2(name,student_id,scholor,salary) values('boyunv03','20211115','senior','500');
insert into test_u2(name,student_id,scholor,salary) values('boyunv04','20211116','college','9000');
--insert into test_u2(name,student_id,scholor,salary) values('boyunv05','20211117','master','30000');
--insert into test_u2(name,student_id,scholor,salary) values('boyunv06','20211118','doctor','60000');
select * from test_u2
创建test_u3和insert语句
CREATE TABLE test_u3(
--主键自增:identity(起始值,增量)
id int identity (1,1) primary key
,name nvarchar(100) null
,student_id nvarchar(100) null
,scholor nvarchar(100) null
,salary int
)
insert into test_u3(name,student_id,scholor,salary) values('boyunv01','20211113','primary','100');
insert into test_u3(name,student_id,scholor,salary) values('boyunv02','20211114','junior','200');
insert into test_u3(name,student_id,scholor,salary) values('boyunv03','20211115','senior','500');
insert into test_u3(name,student_id,scholor,salary) values('boyunv04','20211116','college','9000');
insert into test_u3(name,student_id,scholor,salary) values('boyunv05','20211117','master','30000');
insert into test_u3(name,student_id,scholor,salary) values('boyunv06','20211118','doctor','60000');
select * from test_u3
执行union all 语句
select
select
name,id,salary, sum(salary) as salary
from (
SELECT * FROM test_u1
UNION ALL
SELECT * FROM test_u2
UNION ALL
SELECT * FROM test_u3
)T
GROUP BY id,name,salary
执行结果
在这里插入图片描述
后续补上这后面解释我自己不咋信服~勿喷
标签:salary,name,UNION,scholor,union,student,SQL,test,id 来源: https://blog.csdn.net/weixin_43475992/article/details/121300217
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