sql 使用with as 语句报 “Only `SELECT` statements are allowed against this database”错误

with as 语句又叫CTE,公用表表达式,可以将一个sql语句的结果用一个 变量名来表示,方便后续多次引用。可以用来高性能地简化嵌套sql

参考:https://www.cnblogs.com/fygh/archive/2012/04/25/2160266.html

 

在使用CTE时应注意如下几点:

1. CTE后面必须直接跟使用CTE的SQL语句(如select、insert、update等),否则,CTE将失效。如下面的SQL语句将无法正
常使用CTE:

sql 使用with as 语句报 “Only `SELECT` statements are allowed against this database”错误
with 
cr as
(
select CountryRegionCode from person.CountryRegion where Name like ‘C%‘
)
select * from person.CountryRegion -- 应将这条SQL语句去掉
-- 使用CTE的SQL语句应紧跟在相关的CTE后面--
select * from person.StateProvince where CountryRegionCode in (select * from cr)
sql 使用with as 语句报 “Only `SELECT` statements are allowed against this database”错误

 


2. CTE后面也可以跟其他的CTE,但只能使用一个with,多个CTE中间用逗号(,)分隔,如下面的SQL语句所示:

sql 使用with as 语句报 “Only `SELECT` statements are allowed against this database”错误
with 
cte1 as
(
select * from table1 where name like ‘abc%‘
),
cte2 as
(
select * from table2 where id > 20
),
cte3 as
(
select * from table3 where price < 100
)
select a.* from cte1 a, cte2 b, cte3 c where a.id = b.id and a.id = c.id
sql 使用with as 语句报 “Only `SELECT` statements are allowed against this database”错误

 


3. 如果CTE的表达式名称与某个数据表或视图重名,则紧跟在该CTE后面的SQL语句使用的仍然是CTE,当然,后面的SQL语句
使用的就是数据表或视图了,如下面的SQL语句所示:

sql 使用with as 语句报 “Only `SELECT` statements are allowed against this database”错误
--  table1是一个实际存在的表
with
table1 as
(
select * from persons where age < 30
)
select * from table1 -- 使用了名为table1的公共表表达式
select * from table1 -- 使用了名为table1的数据表
sql 使用with as 语句报 “Only `SELECT` statements are allowed against this database”错误

 


4. CTE 可以引用自身,也可以引用在同一WITH 子句中预先定义的CTE。不允许前向引用。

5. 不能在CTE_query_definition 中使用以下子句:

(1)COMPUTE 或COMPUTE BY

(2)ORDER BY(除非指定了TOP 子句)

(3)INTO

(4)带有查询提示的OPTION 子句

(5)FOR XML

(6)FOR BROWSE


6. 如果将CTE 用在属于批处理的一部分的语句中,那么在它之前的语句必须以分号结尾,如下面的SQL所示:

sql 使用with as 语句报 “Only `SELECT` statements are allowed against this database”错误
declare @s nvarchar(3) 
set @s = ‘C%‘
; -- 必须加分号
with
t_tree as
(
select CountryRegionCode from person.CountryRegion where Name like @s
)
select * from person.StateProvince where CountryRegionCode in (select * from t_tree)

sql 使用with as 语句报 “Only `SELECT` statements are allowed against this database”错误

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