Select data from multiple table
I have the following:
Table1 IdTable1, IdTable2, IdTable3 Table2 IdTable2, Title Table3 IdTable3, FName, LName
I Need the content of Table1 with the Title, FName, LName
I have tried
SELECT T2.Title, T3.FName, T3.LName FROM Table1 T1 LEFT JOIN Table2 T2 ON T1.IdTable2 = T2.IdTable2 LEFT JOIN Table3 T3 ON T1.IdTable3 = T3.IdTable3
All what I get is the Table2 with the other columns NULL or the 2 columns of Table3 with the first column NULL.
Table 1 Contains 1 2 1 2 2 1 3 2 5
Table 2 Contains 1 Mr 2 Madame
Table3 Contains 1 A B 2 C D 3 E F 4 G H 5 I J
The Results of all my Queries are Madame Null Null Madame Null Null Madame Null Null or NULL A B NULL A B NULL I J
Your SQL is fine as long as you want to return partial results.
Have you verified the actual data is correct? You are using a LEFT JOIN. This means rows in T1 will be returned even if there is no matching data in T2 or T3. If there are no matching rows in one of those tables, the columns in that table will be NULL.
If you include all of the columns in T1 in your result set, you will see that there is indeed data in T1, but there is no matching data in T2 or T3. In cases where T3 columns are NULL, that means there is data in T1 and T2 but not T3.
It looks to me like you've got a referential integrity problem. You may need to add foreign keys with drop constraints or fix some application logic problems when creating or deleting records.
I guess your Table1 is a pivot table for Table2 and Table3. I will do something like below.
SELECT T2.Title, T3.FName, T3.LName FROM Table1 T1, Table2 T2, Table3 T3 WHERE T2.IdTable2 = T1.IdTable2 and T3.IdTable3 = T1.IdTable3