The IN (and NOT IN) operators cause the values appearing in the WHERE clause predicate to be tested for membership in a collection of values, represented as a value list or as a subquery.
The syntax for the IN predicate is as follows:
The set of values returned by the SELECT subquery or contained in the value list must be compatible with the data type of x (which is typically a column name). The NULL keyword cannot be included in the value list (for comparisons against null, use a NULL predicate instead). If a SELECT statement (subquery) is used with the IN predicate, the subquery may only return values from a single column. The individual values contained in the value list must be separated by commas.
SELECT sno, sname
WHERE sno IN ('S1', 'S2', 'S3');
All data values in the sno column must match one of the three string constants in order for their corresponding records to be retrieved. This query retrieves the following data values:
sno sname S1 SMITH S2 JONES S3 BLAKE