Sql server 动态查询中的TSQL隔离级别

存储过程中指定的隔离级别是否会执行该存储过程中的动态查询

CREATE PROCEDURE MySP AS 
BEGIN
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
DECLARE @dSQL VARCHAR(max) = 'SELECT col FROM table';
EXEC(@dSQL);
END

---

那么，动态查询中的隔离级别是什么呢？

它会执行动态查询，您可以使用以下内容进行检查：

DBCC useroptions;

SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
DECLARE @dSQL VARCHAR(max) = 'DBCC useroptions';
EXEC(@dSQL);

---

我相信你有隔离级别。我做了这个测试，在动态查询中得到了隔离级别1

-- Create the SP (my test is on AdventureWorks2012)
CREATE PROCEDURE MySP AS 
BEGIN
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
DECLARE @dSQL VARCHAR(max) = 'SELECT * FROM Person.Person; WAITFOR DELAY ''02:00'';';
EXEC(@dSQL);
END

-- Exec SP
EXEC MySP

-- Check the isolation level while your dynamic code is running
SELECT transaction_isolation_level, * FROM sys.sysprocesses t1
JOIN sys.dm_exec_requests t2 on t1.spid = t2.session_id
WHERE t1.spid > 50

---

通常情况下，

SET

语句不仅仅是

事务隔离级别

，

SET

语句是会话级别，因此可以执行到子进程。但是，虽然可以在子流程中更改，但这些更改不会带回调用/父上下文

有关更多详细信息，请参见MSDN页面

通过执行以下操作，您可以轻松测试这一点：

SSMS查询选项卡1:

-- DROP TABLE ##tmp;
CREATE TABLE ##tmp (Col1 INT);
INSERT INTO ##tmp (Col1) VALUES (1);

BEGIN TRAN
SELECT * FROM ##tmp WITH (HOLDLOCK, TABLOCKX);
WAITFOR DELAY '00:02:00.000'; -- 2 minute timer
ROLLBACK TRAN;

-- First, highlight the following and run. It will hang. Cancel the query.
-- SELECT * FROM ##tmp;

-- Second, hit F5. It will return the row twice.
-- If the SET command in the EXEC affected the parent process, the 2nd SELECT
-- would hang.
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;

EXEC (N' SELECT * FROM ##tmp; SET TRANSACTION ISOLATION LEVEL READ COMMITTED;');

SELECT * FROM ##tmp;

SSMS查询选项卡2:

-- DROP TABLE ##tmp;
CREATE TABLE ##tmp (Col1 INT);
INSERT INTO ##tmp (Col1) VALUES (1);

BEGIN TRAN
SELECT * FROM ##tmp WITH (HOLDLOCK, TABLOCKX);
WAITFOR DELAY '00:02:00.000'; -- 2 minute timer
ROLLBACK TRAN;

-- First, highlight the following and run. It will hang. Cancel the query.
-- SELECT * FROM ##tmp;

-- Second, hit F5. It will return the row twice.
-- If the SET command in the EXEC affected the parent process, the 2nd SELECT
-- would hang.
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;

EXEC (N' SELECT * FROM ##tmp; SET TRANSACTION ISOLATION LEVEL READ COMMITTED;');

SELECT * FROM ##tmp;

请参阅：-您可以使用类似的代码对动态sql进行测试。