SQL QUERY - Merge Table

Question

I have a three tables.

Alan1, Alan2, Alan3 are the same in all tables.I want to merge tables. The difference of the tables is the rightmost column. How should I write a SQL Query?

Use JOIN to combine rows with common column values.

Barmar
– Barmar

2020-08-06 23:03:33 +00:00
Commented Aug 6, 2020 at 23:03 — Barmar
– Barmar, Commented Aug 6, 2020 at 23:03

GMB · Accepted Answer · 2020-08-06 23:08:09Z

1

You can join. As commented by Barmar, the idea is to use the first 3 columns as join keys;

select a.*, b.alan4 as alan4b, c.alan4 as alan4c
from a
inner join b
    on  b.alan1 = a.alan1
    and b.alan2 = a.alan2
    and b.alan3 = a.alan3
inner join c
    on  c.alan1 = a.alan1
    and c.alan2 = a.alan2
    and c.alan3 = a.alan3

This gives you rows that are available in all 3 tables. Say you want to allow "missing" rows in b and/or c, then you need to change the two inner joins to left joins.

answered Aug 6, 2020 at 23:08

GMB

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