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CREATE SYNONYM

Updated at: Jul 15, 2020 GMT+08:00

Function

CREATE SYNONYM is used to create a synonym object. A synonym is an alias of a database object and is used to record the mapping between database object names. You can use synonyms to access associated database objects.

Precautions

  • The user of a synonym should be its owner.
  • If the schema name is specified, create a synonym in the specified schema. Otherwise create a synonym in the current schema.
  • Database objects that can be accessed using synonyms include tables, views, functions, and stored procedures.
  • To use synonyms, you must have the required permissions on associated objects.
  • The following DML statements support synonyms: SELECT, INSERT, UPDATE, DELETE, EXPLAIN, and CALL.
  • The CREATE SYNONYM statement of an associated function or stored procedure cannot be used in a stored procedure. You are advised to use synonyms existing in the pg_synonym system catalog in the stored procedure.

Syntax

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CREATE [ OR REPLACE ] SYNONYM synonym_name 
    FOR object_name;

Parameter Description

  • synonym

    Name of a synonym which is created (optionally with schema names)

    Value range: a string. It must comply with the identifier naming rules.

  • object_name

    Name of an object that is associated (optionally with schema names)

    Value range: a string. It must comply with the identifier naming rules.

    object_name can be the name of an object that does not exist.

Examples

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-- Create schema ot.
CREATE SCHEMA ot;

-- Create table ot.t1 and its synonym t1.
CREATE TABLE ot.t1(id int, name varchar2(10)) DISTRIBUTE BY hash(id);
CREATE OR REPLACE SYNONYM t1 FOR ot.t1;

-- Use synonym t1.
SELECT * FROM t1;
INSERT INTO t1 VALUES (1, 'ada'), (2, 'bob');
UPDATE t1 SET t1.name = 'cici' WHERE t1.id = 2;

-- Create synonym v1 and its associated view ot.v_t1.
CREATE SYNONYM v1 FOR ot.v_t1;
CREATE VIEW ot.v_t1 AS SELECT * FROM ot.t1;

-- Use synonym v1.
SELECT * FROM v1;

-- Create overloaded function ot.add and its synonym add.
CREATE OR REPLACE FUNCTION ot.add(a integer, b integer) RETURNS integer AS
$$
SELECT $1 + $2
$$
LANGUAGE sql;

CREATE OR REPLACE FUNCTION ot.add(a decimal(5,2), b decimal(5,2)) RETURNS decimal(5,2) AS
$$
SELECT $1 + $2
$$
LANGUAGE sql;

CREATE OR REPLACE SYNONYM add FOR ot.add;

-- Use synonym add.
SELECT add(1,2);
SELECT add(1.2,2.3);

-- Create stored procedure ot.register and its synonym register.
CREATE PROCEDURE ot.register(n_id integer, n_name varchar2(10))
SECURITY INVOKER
AS
BEGIN
    INSERT INTO ot.t1 VALUES(n_id, n_name);
END;
/

CREATE OR REPLACE SYNONYM register FOR ot.register;

-- Use synonym register to invoke the stored procedure.
CALL register(3,'mia');

-- Delete the synonym.
DROP SYNONYM t1;
DROP SYNONYM IF EXISTS v1;
DROP SYNONYM IF EXISTS v1;
DROP SYNONYM IF EXISTS add;
DROP SYNONYM register;
DROP SCHEMA ot CASCADE;

Helpful Links

ALTER SYNONYM DROP SYNONYM

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