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SQL WHERE Clause

WHERE filters rows with a boolean expression combining comparisons via AND, OR, and NOT, evaluated against each candidate row before grouping. Its predicates are the raw material the optimizer converts into index conditions and filters.

Questions this Concept answers

Why is the `WHERE` clause usually the first place to look in a slow query?

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Filtering Rows with the SQL WHERE Clause Using Comparison, AND, OR, and NOT Operators

The WHERE clause restricts a query's result to the rows for which a stated predicate evaluates to true, so that instead of returning every row of a relation the query returns a subset defined by a co…