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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.
The SQL language is subdivided into several language elements, including: Keywords are words that are defined in the SQL language. They are either reserved (e.g. SELECT, COUNT and YEAR), or non-reserved (e.g. ASC, DOMAIN and KEY). List of SQL reserved words. Identifiers are names on database objects, like tables, columns and schemas. An ...
It was devised by Moshé M. Zloof at IBM Research during the mid-1970s, in parallel to the development of SQL. [1] It is the first graphical query language, using visual tables where the user would enter commands, example elements and conditions. Many graphical front-ends for databases use the ideas from QBE today.
Microsoft SQL Server: SQL Server does not require a dummy table. Queries like 'select 1 + 1' can be run without a "from" clause/table name. [5] MySQL allows DUAL to be specified as a table in queries that do not need data from any tables. [6] It is suitable for use in selecting a result function such as SYSDATE() or USER(), although it is not ...
If a request for data (a SQL Select statement) is sent to the database and a result set is returned, the connection is open but not available for other operations until the client finishes consuming the result set. Other databases, like SQL Server 2005 (and later), do not impose this limitation. However, databases that provide multiple ...
The Jakarta Persistence Query Language (JPQL; formerly Java Persistence Query Language) is a platform-independent object-oriented query language [1]: 284, §12 defined as part of the Jakarta Persistence (JPA; formerly Java Persistence API) specification. JPQL is used to make queries against entities stored in a relational database.
Functions could be used in SELECT statements, provided they do no data manipulation. However, procedures cannot be included in SELECT statements. A stored procedure can return multiple values using the OUT parameter, or return no value. A stored procedure saves the query compiling time. A stored procedure is a database object.
In SQL (Structured Query Language), the term cardinality refers to the uniqueness of data values contained in a particular column (attribute) of a database table. The lower the cardinality, the more duplicated elements in a column. Thus, a column with the lowest possible cardinality would have the same value for every row.