How to create Stored Procedures in PostgreSQL with example?
In this post, you will learn how to use the
CREATE PROCEDURE statement to create new stored procedures in PostgreSQL.
A stored procedure is a bunch of Structured Query Language (SQL) statements with an assigned name, which is stored in a relational database management system as a group, so it tends to be reused. Additionally, the stored procedure doesn't need to have an output.
To define a new stored procedure, you use the create procedure statement. The following shows the basic syntax of the
create procedure statement:
create [or replace] procedure procedure_name(parameter_list) language plpgsql as $$ declare -- variable declaration begin -- stored procedure body end; $$
In this syntax:
To begin with, specify the name of the stored procedure after the
Second, define parameters for the stored procedure. A stored procedure can accept zero or more parameters.
plpgsqlas the procedural language for the stored procedure. Note that you can use other procedural languages for the stored procedure such as SQL, C, etc.
At last, use the dollar-quoted string constant syntax to define the body of the stored procedure.
Parameters in stored procedures can have the
inout modes. But they can't have the
out mode. A stored procedure doesn't a value. You can't utilize the
return statement with a value inside a store procedure like this:
However, you can utilize the
return statement without the expression to stop the stored procedure right away:
If you need to return a value from a stored procedure, you can use parameters with the
PostgreSQL CREATE PROCEDURE statement examples
Here, I will use an
accounts table for the demonstration:
drop table if exists accounts; create table accounts ( id int generated by default as identity, name varchar(100) not null, balance dec(15,2) not null, primary key(id) ); insert into accounts(name,balance) values('Bob',10000); insert into accounts(name,balance) values('Alice',10000);
The following statement shows the data from the
select * from accounts;
The following example creates a stored procedure named
transfer that transfers a specified amount of money from one account to another.
create or replace procedure transfer( sender int, receiver int, amount dec ) language plpgsql as $$ begin -- subtracting the amount from the sender's account update accounts set balance = balance - amount where id = sender; -- adding the amount to the receiver's account update accounts set balance = balance + amount where id = receiver; commit; end;$$
Calling a stored procedure
To call a stored procedure, you use the
CALL statement as follows:
For example, this statement invokes the
transfer stored procedure to transfer
$1,000 from Bob’s account to Alice’s account.
The following statement verifies the data in the
accounts table after the transfer:
SELECT * FROM accounts;
It worked as expected.
create procedurestatement to define a new stored procedure.
callstatement to invoke a stored procedure.
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