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CREATE creates an object (a table, for example) in the database, e.g.: CREATE TABLE example ( column1 INTEGER , column2 VARCHAR ( 50 ), column3 DATE NOT NULL , PRIMARY KEY ( column1 , column2 ) ); ALTER modifies the structure of an existing object in various ways, for example, adding a column to an existing table or a constraint, e.g.:
Limited support for triggers in the MySQL/MariaDB DBMS was added in the 5.0 version of MySQL, launched in 2005. [4] As of version 8.0, they allow for DDL (Data Definition Language) triggers and for DML (Data Manipulation Language) triggers. They also allow either type of DDL trigger (AFTER or BEFORE) to be used to define triggers.
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 ] It is the first graphical query language, using visual tables where the user would enter commands, example elements and conditions.
SQL includes operators and functions for calculating values on stored values. SQL allows the use of expressions in the select list to project data, as in the following example, which returns a list of books that cost more than 100.00 with an additional sales_tax column containing a sales tax figure calculated at 6% of the price.
A HAVING clause in SQL specifies that an SQL SELECT statement must only return rows where aggregate values meet ... $1000 on the date of January 1, 2000, along with ...
The terms schema matching and mapping are often used interchangeably for a database process. For this article, we differentiate the two as follows: schema matching is the process of identifying that two objects are semantically related (scope of this article) while mapping refers to the transformations between the objects.
A relational database management system uses SQL MERGE (also called upsert) statements to INSERT new records or UPDATE or DELETE existing records depending on whether condition matches. It was officially introduced in the SQL:2003 standard, and expanded [ citation needed ] in the SQL:2008 standard.
Reserved words in SQL and related products In SQL:2023 [3] In IBM Db2 13 [4] In Mimer SQL 11.0 [5] In MySQL 8.0 [6] In Oracle Database 23c [7] In PostgreSQL 16 [1] In Microsoft SQL Server 2022 [2]