需要帮助提高 SQL 查询的查询性能

Question

The stored procedure is taking too long to return the results and I want to improve the performance of the stored procedure. But I am not sure where exactly the issue is occurring. Can anyone help by rewriting the subquery after EXISTS clause.

Just for your information, the tables have hundreds of thousands of records

DECLARE @InvNo VARCHAR(MAX) = NULL,

SELECT @InvNo='123'

DECLARE @tblInv TABLE (RowID INT IDENTITY(1,1) PRIMARY KEY CLUSTERED,
                         InvNo VARCHAR(MAX))

IF @InvNo IS NOT NULL
    INSERT INTO @tblInv(InvNo)
    SELECT value
      FROM STRING_SPLIT(@InvNo,',')

 
select * from table1 t
where (@InvNo IS NULL
           OR EXISTS (SELECT 1
                          FROM @tblInv i
                    INNER JOIN table2 inv   
                            ON inv.inv_no = i.InvNo OR ISNULL(inv.alt_inv_no,'@@') = i.InvNo                                
                    INNER JOIN table3 isp
                            ON isp.inv_no = inv.inv_no
                    INNER JOIN table4 ic
                            ON ic.inv_no = inv.inv_no                                               
                         WHERE isp.bl_no = t.bl_no
                           AND ic.cust_code = t.cust_code) 
                )

Answer 1

Without having any additional information, I would suggests splitting the exists into two separate conditions:

select *
from table1 t
where @InvNo IS NULL OR
      EXISTS (SELECT 1
              FROM @tblInv i JOIN
                   table2 inv   
                   ON inv.inv_no = i.InvNo JOIN                              
                   table3 isp
                   ON isp.inv_no = inv.inv_no JOIN
                   table4 ic
                   ON ic.inv_no = inv.inv_no                                               
              WHERE isp.bl_no = t.bl_no AND ic.cust_code = t.cust_code 
             ) OR
     EXISTS (SELECT 1
              FROM @tblInv i JOIN
                   table2 inv   
                   ON inv.alt_inv_no = i.InvNo JOIN                              
                   table3 isp
                   ON isp.inv_no = inv.inv_no JOIN
                   table4 ic
                   ON ic.inv_no = inv.inv_no                                               
              WHERE isp.bl_no = t.bl_no AND ic.cust_code = t.cust_code 
             );

OR usually kills the performance of JOIN s.

Then be sure you have indexes on all the JOIN keys.

Answer 2

Try the below query, Major issue with EXISTS clause and OR clause

As one of the condition in OR clause is with variable we can divide code into two parts and No need to have both IS NULL and exists logics in the same query. It would be good to load the joining columns from exists clause into temp table and inner join with major table might give better performance.

SELECT @InvNo='123'

DECLARE @tblInv TABLE 
(RowID INT IDENTITY(1,1) PRIMARY KEY CLUSTERED, InvNo VARCHAR(MAX))
     
IF @InvNo IS NULL
BEGIN
    select * from table1 t
END
ELSE
BEGIN
    INSERT INTO @tblInv(InvNo)
    SELECT value FROM STRING_SPLIT(@InvNo,',')
    
SELECT DISTINCT isp.bl_no,ic.cust_code INTO #T
      FROM @tblInv i
    INNER JOIN table2 inv   
            ON inv.inv_no = i.InvNo                              
    INNER JOIN table3 isp
            ON isp.inv_no = inv.inv_no
    INNER JOIN table4 ic
            ON ic.inv_no = inv.inv_no
UNION
SELECT DISTINCT isp.bl_no,ic.cust_code
      FROM @tblInv i
    INNER JOIN table2 inv   
            ON ISNULL(inv.alt_inv_no,'@@') = i.InvNo                                
    INNER JOIN table3 isp
            ON isp.inv_no = inv.inv_no
    INNER JOIN table4 ic
            ON ic.inv_no = inv.inv_no

    select * from table1 t
    INNER JOIN #T T2 ON T2.bl_no = t.bl_no AND T2.cust_code = t.cust_code
END