---json
{
    "name": "Sql DDL",
    "page_id": "qu5u64zpffjr2qyj3tjng"
}
---
====== SQL - Data Definition Language (DDL) ======


===== About =====
''DDL'' is a [[:docs:system:database:sql_statement#subset|sql subset]] that manages the [[:docs:resource:metadata|database metadata]].



You can execute ''DDL'' statements with a [[docs:resource:sql_request|SQL Request]].

===== Example/HowTo =====


  * [[howto/sql_query/dml_query]]
  * [[howto/postgres/create_table_script]]
===== List =====

  * ''CREATE'',
  * ''ALTER'',
  * ''DROP''

===== DDL vs the CREATE operation =====


With a ''DDL'', you create a SQL Object with the ''CREATE'' statement with the [[:docs:op:create|create]] operation, you can
  * ''create table'' by copy
  * ''create view'' from a list of files containing ''Select'' statements.
===== Execution =====

If you execute a [[docs:resource:sql_request|SQL fetch]] that contains ''DDL'' statements, you will get the following results.


<file>
id          count   statement                                              error_code   error_message
--   ------------   ----------------------------------------------------   ----------   -------------
 1              0   create table ddl_table_test\n(\n    column_name inte            0
 2              0   alter table ddl_table_test\n    owner to postgres;\n            0
</file>

A ''DDL'' script is an [[docs:resource:runtime#execution|runtime]] and therefore is executed:
  * at access/runtime
  * or via the [[:docs:op:execute|execute operation]]

Example of execution at runtime
  * with the [[:docs:op:print|print command]]. If you print it 2 times, they will execute 2 times.
<code bash>
tabul data print (create_ddl.sql@cd)@sqlite
</code>
===== Note =====
==== Auto-commit ====

''DDL'' statements auto-commit, so they can't be rolled back