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  2. W3Schools - Wikipedia

    en.wikipedia.org/wiki/W3Schools

    Current status. Active. W3Schools is a freemium educational website for learning coding online. [1] [2] Initially released in 1998, it derives its name from the World Wide Web but is not affiliated with the W3 Consortium. [3] [4] W3Schools offers courses covering many aspects of web development. [5] W3Schools also publishes free HTML templates.

  3. SQL syntax - Wikipedia

    en.wikipedia.org/wiki/SQL_syntax

    SQL syntax. The syntax of the SQL programming language is defined and maintained by ISO/IEC SC 32 as part of ISO/IEC 9075. This standard is not freely available. Despite the existence of the standard, SQL code is not completely portable among different database systems without adjustments.

  4. Correlated subquery - Wikipedia

    en.wikipedia.org/wiki/Correlated_subquery

    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. Because the subquery may be evaluated once for each row processed by the outer query, it can be slow.

  5. Join (SQL) - Wikipedia

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

    Join (SQL) A Venn diagram representing the full join SQL statement between tables A and B. A join clause in the Structured Query Language ( SQL) combines columns from one or more tables into a new table. The operation corresponds to a join operation in relational algebra. Informally, a join stitches two tables and puts on the same row records ...

  6. SQL - Wikipedia

    en.wikipedia.org/wiki/SQL

    History. SQL was initially developed at IBM by Donald D. Chamberlin and Raymond F. Boyce after learning about the relational model from Edgar F. Codd in the early 1970s. This version, initially called SEQUEL (Structured English Query Language), was designed to manipulate and retrieve data stored in IBM's original quasirelational database management system, System R, which a group at IBM San ...

  7. Having (SQL) - Wikipedia

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

    WHERE is taken into account at an earlier stage of a query execution, filtering the rows read from the tables. If a query contains GROUP BY, rows from the tables are grouped and aggregated. After the aggregating operation, HAVING is applied, filtering out the rows that don't match the specified conditions. Therefore, WHERE applies to data read ...

  8. Stored procedure - Wikipedia

    en.wikipedia.org/wiki/Stored_procedure

    Stored procedure. A stored procedure (also termed prc, proc, storp, sproc, StoPro, StoredProc, StoreProc, sp, or SP) is a subroutine available to applications that access a relational database management system (RDBMS). Such procedures are stored in the database data dictionary . Uses for stored procedures include data-validation (integrated ...

  9. Select (SQL) - Wikipedia

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

    Select (SQL) The SQL SELECT statement returns a result set of rows, from one or more tables. [1] [2] A SELECT statement retrieves zero or more rows from one or more database tables or database views. In most applications, SELECT is the most commonly used data manipulation language (DML) command. As SQL is a declarative programming language ...

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