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Databases :: MySql :: INSERT...SELECT from multiple tables
By: javaQQ U.S.A.  Date: 18/06/2003 00:00:00  English  Points: 100 Status: Answered
Quality : Excellent
Is the following code valid for MySQL?

INSERT INTO Summary( column1, column2, column3, column4 )
SELECT a.one_field, a.another_field, b.field_one, c.field_two
FROM Table_One AS a, Table_Two AS b, Table_Three AS c
WHERE Table_One.common = Table_Two.common
AND Table_Two.common = Table_Three.common
AND Table_Three.common = Table_One.common

Please critique.

Many thanks in advance
By: VGR Date: 18/06/2003 08:04:00 English  Type : Comment
yes, I think so. It even looks pretty very good :D
By: TroyK Date: 18/06/2003 09:04:00 English  Type : Answer
javaQQ;

How about using your table aliases in your JOINs...

INSERT INTO Summary( column1, column2, column3, column4 )
SELECT a.one_field, a.another_field, b.field_one, c.field_two
FROM Table_One AS a, Table_Two AS b, Table_Three AS c
WHERE a.common = b.common
AND b.common = c.common
AND c.common = a.common --I think this AND condition is unneccessary

Makes it a bit more readable.

VGR;

Point of curiosity... does MySQL support ANSI join syntax? e.g.:

INSERT INTO Summary( column1, column2, column3, column4 )
SELECT a.one_field, a.another_field, b.field_one, c.field_two
FROM Table_One AS a
INNER JOIN Table_Two AS b ON a.common = b.common
INNER JOIN Table_Three AS c ON b.common = c.common

If so, javaQQ, you may want to get in the habit of using the ANSI JOIN syntax as the differences become important when doing OUTER JOINs (but not in your sample)

HTH,
TroyK, MCSD
By: JakobA Date: 18/06/2003 11:05:00 English  Type : Comment
Yes you can do those inner joins in mysql <A HREF="http://www.mysql.com/doc/en/JOIN.html">http://www.mysql.com/doc/en/JOIN.html</a>
By: VGR Date: 18/06/2003 14:34:00 English  Type : Assist
yes, but it's not necessary. mysql is more ansi-compliant than m$-sql server, the proprietary thingy from merdu$oft
By: psadac Date: 19/06/2003 03:26:00 English  Type : Assist
one more :

INSERT INTO Summary
SELECT a.one_field AS column1, a.another_field AS column2, b.field_one AS column3, c.field_two AS column4
FROM Table_One a INNER JOIN Table_Two b USING(common)
INNER JOIN Table_Three c USING(common)
By: javaQQ Date: 19/06/2003 08:46:00 English  Type : Comment
Two points:

ONE:
>How about using your table aliases in your JOINs...
>...
>WHERE a.common = b.common
>AND b.common = c.common
>AND c.common = a.common --I think this AND condition is unneccessary

Are you sure that that is allowed?
According to the MySQL Pocket Reference (O'Reilly), p. 57,
"You cannot use aliases in WHERE clauses as their values cannot be calculated at that point"

TWO:
Regarding the points: My impulse is to just split them four ways. Are there any objections to that?

Many thanks for the responses so far.
By: TroyK Date: 19/06/2003 09:49:00 English  Type : Comment
javaQQ;

>>"You cannot use aliases in WHERE clauses as their values cannot be calculated at that point"

I think this is refering to aliased _column_ names. e.g., you can't do this:

SELECT col1 AS MyColumnName
FROM MyTable
WHERE MyColumnName = 1

I could be wrong, though, as my expertise lies more with MS SQL Server (T-SQL). I'd say give it a try.

Re: the points, IMO, you should split them among any of the participants who were able to help.

TroyK, MCSD
By: JakobA Date: 20/06/2003 05:04:00 English  Type : Assist
Table aliases are legal anywhere in the sql command

Fied-value aliases are legal only after the group by clause (before that thay may not have a meaning as in COUNT(field) AS nr, )
By: JakobA Date: 20/06/2003 05:15:00 English  Type : Comment
According to the mysql documentation you can even use field value aliases IN the group by clause.
<A HREF="http://www.mysql.com/doc/en/Problems_with_alias.html">http://www.mysql.com/doc/en/Problems_with_alias.html</a>

I think that would fail where the field is an accumulated value depending on grouping ( COUNT, SUM, MIN, ...)

When it is not the alias is at least possible there.

regards JakobA
By: javaQQ Date: 20/06/2003 05:32:00 English  Type : Comment
Thanks for all the responses.
I have increased the points to 100 and split them four ways.

Many thanks again.

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