Considerations for SQL Server

1, the use of nolock
NOLOCK will corrupt database connection transaction ISOLATION LEVEL

Test as follows
Create a window in SQL Server's management Studio and execute the following statement
BEGIN TRANSACTION
INSERT into T1 (F1) VALUES (1)

Create a new window and execute the following statement
SELECT * from t1 where f1 = 1
The query is blocked at this time (block)

SELECT * from T1 (NOLOCK)
At this point the query executes and queries for uncommitted insert data. Equivalent to the statement running under the transaction isolation level of dirty read