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mysqlsqlsyntaxwhere-clause
Fi Horan
Fi Horan

Reputation: 512

Mysql where clause syntax

I was running through some of our code at work and came across this structure for an sql query and was sure it was a typo in the variables of our PHP, I ran it and it works.

Select column from table where value = column;

Anyone I know was always taught the correct syntax is:

Select column from table where column = value;

Is there any reason for this being legal, other than SQL just checks are both sides of an equation equal to each other? I'm more posting this because I found it really interesting, like a 'the more you know' kind of thing.

Upvotes: 4

Views: 221

Answers (3)

Tu4n3r
Tu4n3r

Reputation: 441

The syntax of an SQL query is :

SELECT what_to_select
FROM which_table
WHERE conditions_to_satisfy;

You can use any condition you want, for example : 

SELECT * FROM table WHERE 1

will return you all the rows

while

SELECT * FROM table WHERE 0

will return you nothing

after a WHERE you must have a condition, nothing else

Upvotes: 1

Mureinik
Mureinik

Reputation: 312116

The equality operator (=) is symmetric - if a=b is true, then so is b=a. a and b can be column names, values or complex expressions. It's common to use the form column=value, but syntactically speaking, it's completely equivalent to value=column.

Upvotes: 4

Greg Viers
Greg Viers

Reputation: 3523

Yes, you have it right sql just checks both sides of an equation. The equation could even contain a column on neither side! such as

SELECT column from table where 1=2;

Upvotes: 1

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