sql query join query output gives duplicates

Question

So i wanted to extract information from 3 tables at the same time, but whenever i update my query on table1 it gives me duplicates and overrides the previous entries, like in row n in garage column if i update garage to red, it will display red for the previous entry as well. any thoughts on how to do this?

SELECT `date`,`tagid`,`garage`,`class` 
FROM table1 JOIN table2 ON table1.number = table2.tagid
UNION SELECT `date`,`tagid`,`garage`,`class` 
FROM table1 JOIN table3 ON table1.number = table3.tagid

A UNION by definition removes all duplicates from your resultset so the statement you've presented can't possibly contain duplicates. Without additional information as asked by @PugganSe, we can only guess what it is you really want. The statement whenever I update my query on table1 it gives me duplicates ... like in row n doesn't make any sense to me. — Lieven Keersmaekers
– Lieven Keersmaekers, Commented Aug 1, 2012 at 6:33

Puggan Se · Accepted Answer · 2012-08-01 05:54:11Z

1

It looks like you want to do somthing like:

SELECT date, tagid, garage, class 
FROM table1 
LEFT JOIN (
    SELECT date, tagid, garage, class FROM table2 
    UNION
    SELECT date, tagid, garage, class FROM table3 
) AS table_2_and_3 ON (table1.number = table_2_and_3.tagid)

you may need to remove some fields on row 4 and 6 if they are in table 1.

answered Aug 1, 2012 at 5:54

Puggan Se

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