enow.com Web Search

Search results

  1. Results from the WOW.Com Content Network
  2. SQL syntax - Wikipedia

    en.wikipedia.org/wiki/SQL_syntax

    The OFFSET clause specifies the number of rows to skip before starting to return data. The FETCH FIRST clause specifies the number of rows to return. Some SQL databases instead have non-standard alternatives, e.g. LIMIT, TOP or ROWNUM. The clauses of a query have a particular order of execution, [5] which is denoted by the number on the right ...

  3. Correlated subquery - Wikipedia

    en.wikipedia.org/wiki/Correlated_subquery

    In a SQL database query, a correlated subquery (also known as a synchronized subquery) is a subquery (a query nested inside another query) that uses values from the outer query. This can have major impact on performance because the correlated subquery might get recomputed every time for each row of the outer query is processed.

  4. Join (SQL) - Wikipedia

    en.wikipedia.org/wiki/Join_(SQL)

    Conversely, an inner join can result in disastrously slow performance or even a server crash when used in a large volume query in combination with database functions in an SQL Where clause. [2] [3] [4] A function in an SQL Where clause can result in the database ignoring relatively compact table indexes. The database may read and inner join the ...

  5. Select (SQL) - Wikipedia

    en.wikipedia.org/wiki/Select_(SQL)

    SELECT is the most complex statement in SQL, with optional keywords and clauses that include: The FROM clause, which indicates the tables to retrieve data from. The FROM clause can include optional JOIN subclauses to specify the rules for joining tables. The WHERE clause includes a comparison predicate, which restricts the rows returned by the ...

  6. Query by Example - Wikipedia

    en.wikipedia.org/wiki/Query_by_Example

    Example of QBE query with joins, designed in Borland's Paradox database. Query by Example (QBE) is a database query language for relational databases.It was devised by Moshé M. Zloof at IBM Research during the mid-1970s, in parallel to the development of SQL. [1]

  7. Where (SQL) - Wikipedia

    en.wikipedia.org/wiki/Where_(SQL)

    WHERE clauses are not mandatory clauses of SQL DML statements, but can be used to limit the number of rows affected by a SQL DML statement or returned by a query. In brief SQL WHERE clause is used to extract only those results from a SQL statement, such as: SELECT , INSERT , UPDATE , or DELETE statement.

  8. Having (SQL) - Wikipedia

    en.wikipedia.org/wiki/Having_(SQL)

    HAVING and WHERE are often confused by beginners, but they serve different purposes. WHERE is taken into account at an earlier stage of a query execution, filtering the rows read from the tables.

  9. Merge (SQL) - Wikipedia

    en.wikipedia.org/wiki/Merge_(SQL)

    IBM Db2 extends the syntax with multiple WHEN MATCHED and WHEN NOT MATCHED clauses, distinguishing them with ... AND some-condition guards. Microsoft SQL Server extends with supporting guards and also with supporting Left Join via WHEN NOT MATCHED BY SOURCE clauses. PostgreSQL supports merge since version 15 but previously supported merging via ...