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  2. SQL syntax - Wikipedia

    en.wikipedia.org/wiki/SQL_syntax

    SELECT is the most complex statement in SQL, with optional keywords and clauses that include: The FROM clause, which indicates the table(s) 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 ...

  3. 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 ...

  4. 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.

  5. From (SQL) - Wikipedia

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

    From clauses are very common, and will provide the rowset to be exposed through a Select statement, the source of values in an Update statement, and the target rows to be deleted in a Delete statement. [1] FROM is an SQL reserved word in the SQL standard. [2] The FROM clause is used in conjunction with SQL statements, and takes the following ...

  6. 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 ...

  7. Having (SQL) - Wikipedia

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

    A HAVING clause in SQL specifies that an SQL SELECT statement must only return rows where ... To view the present condition formed by the GROUP BY clause, the HAVING ...

  8. Category:SQL keywords - Wikipedia

    en.wikipedia.org/wiki/Category:SQL_keywords

    Category: SQL keywords. 5 languages. ... This category lists articles about SQL statements, clauses, and keywords. See also. List of SQL reserved words;

  9. 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.