what is correct sql statement syntax in PHP?

when I write a sql statement in php, i usualy write it as below

SELECT COUNT(*) FRO开发者_开发百科M catalogsearch_query AS main_table

but I found that some people write sql statement like

SELECT COUNT(*) FROM `catalogsearch_query` AS `main_table`

do I have to use ` ?

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You don't have to use backticks. However when you're using reserved keywords as table or field names, then you have to enclose them in backticks for them to work.

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From MySql docs:

Database, table, index, column, and alias names are identifiers. An identifier may be quoted or unquoted. If an identifier contains special characters or is a reserved word, you must quote it whenever you refer to it.

We use the backtick ` for quoting.