3.1. The same piece of code, running in a stored procedure is dozens of times slower than ordinary SQL

question:

The same piece of code, running in a stored procedure is dozens of times slower than ordinary SQL execution

principle:

In SQL Server there is a feature called "Parameter sniffing" parameter sniffing. SQL Server will formulate an execution plan before the stored procedure is executed, resulting in slower speed.

Solution:

1. Create a variable in the stored procedure to replace the parameter

CREATE  PROC sp_yp_jxctj
     @varTemp1  VARCHAR ( 50 )
 AS 
    BEGIN 
-- replace parameters with variables to prevent "Parameter sniffing" problems 
        DECLARE  @var1  VARCHAR ( 50 ) =  @varTemp1  
-- references to parameters below refer to @var1 , don't quote @varTemp1

    END; 

2. Hide the affected SQL statements, such as:

   a) Put the affected sql statement in a sub-stored procedure, for example, we can call a word stored procedure after @thedate is set to today and pass in @thedate as a parameter.

   b) Use sp_executesql to execute the affected sql. The execution plan will not be executed unless the sp_executesql statement is executed.

   c) Use dynamic sql ("EXEC(@sql)" to execute the affected sql.