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I was wondering why MYSQL uses a single equals sign in conditional statements instead of the more typical two equals signs. Is there a technical/historical reason for this? Thanks.
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SQL is a declarative language, and assignments are not typically made in SQL queries themselves. As a result, SQL doesn't have the problem of ambiguity of = meaning either assignment or equality check. As a result, there is no problem with using = to check equality.
In MySQL, you can use the = operator to test for equality in a query. The = operator can only test equality with values that are not NULL. For example: SELECT * FROM contacts WHERE last_name = 'Johnson';
There is no double equal sign concept. It can be used to compare two values. If you use double equal sign(==) in MySQL, you will get an error message.
Hi, I was wondering why MYSQL uses a single equals sign in conditional statements instead of the more typical two equals signs. Is there a technical/historical reason for this? Thanks.
Comparison is much more common in SQL than assignment.
That's why SQL uses more short syntax to do more common things.
In classical SQL, comparison can be distinguished from assignment by context (assignment can be only in SET clause of an UPDATE statement), that's why one operator can be used for both operations.
In MySQL's extension to SQL, assignment to a session variable is denoted by :=
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More like historical.
It's SQL. It has used a single equals sign for comparison since the early '70s.
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