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23 de may. de 2023 · A. Utilizar NULL en una subconsulta para seguir devolviendo un conjunto de resultados. En el ejemplo siguiente se devuelve un conjunto de resultados con NULL especificado en la subconsulta, que se sigue evaluando como TRUE al utilizar EXISTS. SQL. Copiar.
Learn how to use the SQL EXISTS operator to test for the existence of any record in a subquery. See syntax, examples and a demo database with products and suppliers.
Aprende a usar la cláusula WHERE EXISTS en SQL para filtrar datos mediante subconsultas. Encuentra ejemplos de cómo aplicar el operador EXISTS con el operador IF y con tablas relacionadas.
The $exists operator matches documents that contain or do not contain a specified field, including documents where the field value is null.
18 de nov. de 2013 · The EXISTS operator returns true if the subquery returns at least one record and false if no row is selected. The database engine does not have to run the subquery entirely. If a single record is matched, the EXISTS operator returns true, and the associated other query row is selected.
The SQL EXISTS condition is used in combination with a subquery and is considered to be met, if the subquery returns at least one row. It can be used in a SELECT, INSERT, UPDATE, or DELETE statement.
The EXISTS operator returns true if the subquery contains any rows. Otherwise, it returns false. The EXISTS operator terminates the query processing immediately once it finds a row, therefore, you can leverage this feature of the EXISTS operator to improve the query performance.
