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Does a foreign key automatically create an index?
... I'm just about positive that PostgreSQL creates an index. I'm pretty sure MySQL does. Making the index makes a ton of sense, but IT'T NOT REQUIRED. After all, why reference something if every time the DB goes to look it up it has to do a tablescan?
– MBCook
Ma...
Null vs. False vs. 0 in PHP
...or a data value that doesn't exist in the database or is unknown. See dev.mysql.com/doc/refman/5.0/en/working-with-null.html or en.wikipedia.org/wiki/Null_%28SQL%29.
– Eli
Dec 5 '12 at 3:39
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Getting the PublicKeyToken of .Net assemblies
...Pravat> ([system.reflection.assembly]::loadfile("C:\Program Files (x86)\MySQL\Connector NET 6.6.5\Assemblies\v4.0\MySql.Data.dll")).FullName
like
PS C:\Users\Pravat> ([system.reflection.assembly]::loadfile("dll full path")).FullName
and will appear like
MySql.Data, Version=6.6.5.0, Cu...
SQL - using alias in Group By
...OUP BY is executed before the SELECT clause.
There are exceptions though: MySQL and Postgres seem to have additional smartness that allows it.
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Cleanest way to build an SQL string in Java
...d MERGE. You can create SQL like this:
String sql1 = DSL.using(SQLDialect.MYSQL)
.select(A, B, C)
.from(MY_TABLE)
.where(A.equal(5))
.and(B.greaterThan(8))
.getSQL();
String sql2 = DSL.using(SQLDialect.MYSQL)
...
What's the longest possible worldwide phone number I should consider in SQL varchar(length) for phon
...
I know that should be the case, but it's not always. In MySQL (for example) the full length is used for sorting. It's best to apply at least some minimal effort.
– Morgan Tocker
Jul 20 '10 at 18:23
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How to UPSERT (MERGE, INSERT … ON DUPLICATE UPDATE) in PostgreSQL?
... very frequently asked question here is how to do an upsert, which is what MySQL calls INSERT ... ON DUPLICATE UPDATE and the standard supports as part of the MERGE operation.
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INNER JOIN ON vs WHERE clause
....
It's easier to see this with the WHERE syntax.
As for your example, in MySQL (and in SQL generally) these two queries are synonyms.
Also note that MySQL also has a STRAIGHT_JOIN clause.
Using this clause, you can control the JOIN order: which table is scanned in the outer loop and which one is...
Best way to do multi-row insert in Oracle?
...rform multi-row inserts into an Oracle 9 database. The following works in MySQL but doesn't seem to be supported in Oracle.
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How to get multiple counts with one SQL query?
... entire nested query with a simple count(*) as @Mihai shows - with further MySQL only syntax simplifications.
– YoYo
Apr 1 '17 at 19:29
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