SQL Server Conditional Joins

user_6146170 0
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I've three tables Table1 Table2 Table3. I've to perform some operations on them and store the resultant in Table4

Table1: 

ID       t1col2     t1col3  
``````   ``````     ``````
123      Fname1     Lname1
456      Fname2     Lname2  
789      Fname3     LnameAA

Table2: 

ID        t2col2     t2col3     t2col4
`````     ``````     ``````     ``````
122       Fname1     Lname1     String1
466       Fname2     Lname2     String2
789       Fname3     Lname3     String3

Table3: 

ID       t3col2       
``````   ``````      
122      querty     
789      asdfgh

How can I perform conditional joins to check for following conditions:

  • Search for a substring AA in t1col3.
  • If found, replace t1col3 value from Table1 with t2col3 value from Table2 only when Table1 ID and Table2 ID are equal.
  • From the above result, search for matching ID in Table3
  • If found, display the content in Table4 as mentioned below.

Expected output:

Table4:

ID         t1col2     t2col3     t2col4     t3col2  
```````    ```````    ```````    ```````    ```````  
789        Fname3     Lname3     String3    asdfgh
outer-join inner-join sql-server
3 Answers

First insert them in Table4.

Then correct Table1 based on Table4. 

DELETE FROM Table4;

INSERT INTO Table4 (ID, t1col2, t2col3, t2col4, t3col2)
SELECT t2.ID, t1.t1col2, t2.t2col3, t2.t2col4, t3.t3col2
FROM Table2 t2
JOIN Table1 t1 ON t1.ID = t2.ID AND t1.t1col3 LIKE '%AA%'
JOIN Table3 t3 ON t3.ID = t1.ID;

UPDATE t1
SET t1col3 = t4.t2col3
FROM Table1 t1
JOIN Table4 t4 ON t4.ID = t1.ID
WHERE t1.t1col3 != t4.t2col3;

SELECT * 
FROM Table4 
ORDER BY ID;

Test on db<>fiddle here

Result: 

ID      t1col2      t2col3      t2col4      t3col2
----    --------    --------    --------    --------
789     Fname3      Lname3      String3     asdfgh
user_40034190

can you try this

SELECT T1.ID , T1COL2, T2COL3, T2COL4, T3COL2
FROM TABLE2 AS T2
INNER JOIN TABLE1 AS T1 
  ON T2.ID = T1.ID AND T1.T1COL3 LIKE '%AA' 
INNER JOIN TABLE3 AS T3
  ON T3.ID = T2.ID

Fiddle Link

user_11189780 
Select Table1.ID, Table1.T1col2, Table2.T2col3, Table2.T2col4, Table3.T3col2
From Table1
Inner join Table2 on Table1.ID = Table2.ID AND Table1. t1col3 like ‘%AA%’ 
Inner join Table3 on Table1.ID = Table3.ID

Sorry but i didn’t understand what you want by : «  If found, replace t1col3 value from Table1 with t2col3 value from Table2 only when Table1 ID and Table2 ID are equal. » You want update value on table1 ?

user_99408030
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