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Many data description languages use a declarative syntax to define columns and data types. Structured Query Language (SQL), however, uses a collection of imperative verbs whose effect is to modify the schema of the database by adding, changing, or deleting definitions of tables or other elements.
In relational databases a virtual column is a table column whose value(s) is automatically computed using other columns values, or another deterministic expression. Virtual columns are defined of SQL:2003 as Generated Column, [1] and are only implemented by some DBMSs, like MariaDB, SQL Server, Oracle, PostgreSQL, SQLite and Firebird (database server) (COMPUTED BY syntax).
In table T, set the value of column C1 to 9 and the value of C3 to 4 for all rows for which the value of column C2 is "a". UPDATE T SET C1 = 9 , C3 = 4 WHERE C2 = 'a' Increase value of column C1 by 1 if the value in column C2 is "a".
Tables, a set of values organized into rows and columns; Indexes, a data structure providing faster queries (at the expense of slower writing and storage to maintain the index structure) Views, a virtual table that is made as it is queried; Synonyms, alternate names for a table, view, sequence or other object in a database
The query retrieves all rows from the Book table in which the price column contains a value greater than 100.00. The result is sorted in ascending order by title. The asterisk (*) in the select list indicates that all columns of the Book table should be included in the result set.
If the last name is larger than 10 letters, using the SUBSTR function [9] we change the last_name column value to an abbreviation. CREATE OR REPLACE TRIGGER phone_book_insert BEFORE INSERT ON phone_book FOR EACH ROW WHEN ( LENGTH ( new . last_name ) > 10 ) BEGIN : new . last_name : = SUBSTR (: new . last_name , 0 , 1 ); END ;
Transact-SQL (T-SQL) is Microsoft's and Sybase's proprietary extension to the SQL (Structured Query Language) used to interact with relational databases.T-SQL expands on the SQL standard to include procedural programming, local variables, various support functions for string processing, date processing, mathematics, etc. and changes to the DELETE and UPDATE statements.
In SQL, the data manipulation language comprises the SQL-data change statements, [3] which modify stored data but not the schema or database objects. Manipulation of persistent database objects, e.g., tables or stored procedures, via the SQL schema statements, [3] rather than the data stored within them, is considered to be part of a separate data definition language (DDL).