Are square brackets valid in an SQL query?

Question

I am looking at a note that someone wrote to me and it looks something like this:

SELECT Something FROM Foobar WHERE blah='blah'  --- [pulls this too - SELECT Something FROM Foobar WHERE something='elsehappens']

I'm trying to figure out if the --- [ comment - QUERY] is just a comment or if it actually means something I haven't seen before.

score 3 · Accepted Answer · answered Jan 11 '10 at 18:23

3

In this case it is just a comment... square brackets are often used to delimit real names for reserved words, or simply to delimit actual identifiers, but anything after a -- is always a comment.

answered Jan 11 '10 at 18:23

Michael Bray

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Brackets are also used to treat space-separated words as one. E.G. if a column is called Text Entry you would have to do SELECT * FROM [Text Entry] – Nick Jan 11 '10 at 18:25
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@Nick, that's dependent on the SQL server, though. I believe MySQL uses back ticks instead of square brackets. – Paul Tomblin Jan 11 '10 at 18:26
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anything after -- on the same line is always a comment – D'Arcy Rittich Jan 11 '10 at 18:26
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Can also to be used as character classes in an regex like expressions: `SELECT * FROM Table WHERE field like 'caf[eéèëê]'` – Rubens Farias Jan 11 '10 at 18:28

score 0 · Answer 2 · answered Jan 11 '10 at 18:26

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They are generally used to indicate optional words or clauses. In this example, it appears to be nothing more than a comment as indicated in the manual: MySQL Comment Syntax

answered Jan 11 '10 at 18:26

Sampson

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score 0 · Answer 3 · answered Jan 11 '10 at 18:36

In MySQL, a -- comment is just a comment.

C-style comments with special characters may be used to give hints to the query optimizer, run version-specific queries etc:

CREATE TABLE mytable (id INT) /*!50000 ENGINE=InnoDB */ ;

This will create the table as InnoDB in MySQL 5.0 or higher, or with default engine in MySQL below 5.0.

Are square brackets valid in an SQL query?

3 Answers3

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