Matching a Value with Subqueries
Subqueries can be used in the WHERE clause as the left side of an expression following one of the comparison operators shown in Table 6.1. A subquery that is used with a comparison operator must return a single value rather than a list of values. If such a subquery returns more than one value, the server will display an error message.
| Operator | Description |
|---|---|
| = | Equality |
| <> | Not equal |
| > | Greater than |
| >= | Greater than or equal |
| < | Less than |
| !> | Not greater than |
| !< | Not less than |
| <= | Less than or equal |
You would use a subquery with a comparison operator to select a value from either another table or the same table. You will realize rather quickly that subqueries will make your ...
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