What are the difference between DDL, DML and DCL commands?
DDL – Data Definition Language: statements used to define the database structure or schema. Some examples: • CREATE – to create objects in the database • ALTER – alters the structure of the database • DROP – delete objects from the database • TRUNCATE – remove all records from a table, including all spaces allocated for the records are removed • COMMENT – add comments to the data dictionary • RENAME – rename an object DML – Data Manipulation Language: statements used for managing data within schema objects. Some examples: • SELECT – retrieve data from the a database • INSERT – insert data into a table • UPDATE – updates existing data within a table • DELETE – deletes all records from a table, the space for the records remain • MERGE – UPSERT operation (insert or update) • CALL – call a PL/SQL or Java subprogram • EXPLAIN PLAN – explain access path to data • LOCK TABLE – control concurrency DCL – Data Control Language. Some examples: • GRANT – gives user’s access privileges to database
DDL – Data Definition Language: statements used to define the database structure or schema. Some examples: • CREATE – to create objects in the database • ALTER – alters the structure of the database • DROP – delete objects from the database • TRUNCATE – remove all records from a table, including all spaces allocated for the records are removed • COMMENT – add comments to the data dictionary • RENAME – rename an object DML – Data Manipulation Language: statements used for managing data within schema objects. Some examples: • SELECT – retrieve data from the a database • INSERT – insert data into a table • UPDATE – updates existing data within a table • DELETE – deletes all records from a table, the space for the records remain • MERGE – UPSERT operation (insert or update) • CALL – call a PL/SQL or Java subprogram • EXPLAIN PLAN – explain access path to the data • LOCK TABLE – controls concurrency DCL – Data Control Language. Some examples: • GRANT – gives user’s access privileges to data