How to create a function in PostgreSQL?

@cortez.connelly 

To create a function in PostgreSQL, you can use the CREATE FUNCTION statement. Here is the general syntax:

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CREATE FUNCTION function_name(parameter_list)
RETURNS return_type
AS $$
BEGIN
  -- function body goes here
END;
$$ LANGUAGE language_name;

Here is an example that creates a function that calculates the area of a rectangle given its length and width:

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CREATE FUNCTION calc_rect_area(length float, width float)
RETURNS float
AS $$
BEGIN
  RETURN length * width;
END;
$$ LANGUAGE plpgsql;

This function can be called as follows:

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SELECT calc_rect_area(2.5, 3.7);

This would return the result 9.25.

You can also specify the parameters as IN, OUT, or INOUT to indicate their direction (input, output, or both). For example:

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CREATE FUNCTION swap(IN x int, INOUT y int)
RETURNS void
AS $$
BEGIN
  y := x;
  x := y;
END;
$$ LANGUAGE plpgsql;

This function can be called as follows:

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SELECT swap(1, 2);

This would return no result, but the values of x and y would be swapped within the function.

I hope this helps! Let me know if you have any questions.

@cortez.connelly 

To create a function in PostgreSQL, you can follow these steps:

1. Connect to your PostgreSQL server using a client tool like psql or a graphical tool like pgAdmin.
2. Choose a database where you want to create the function. You can use the c command in psql to connect to a specific database.
3. Write the function code using the SQL language. Here's an example of a simple function that returns the sum of two numbers:

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CREATE FUNCTION sum_numbers(a INTEGER, b INTEGER) 
  RETURNS INTEGER 
AS $$
BEGIN
  RETURN a + b;
END;
$$ LANGUAGE plpgsql;

In the above example, sum_numbers is the name of the function, and it takes two integer parameters a and b. The RETURNS INTEGER statement indicates that the function will return an integer value. The actual logic of the function is written inside the BEGIN and END block.

1. Execute the CREATE FUNCTION statement. If there are no syntax errors, PostgreSQL will create the function and show a success message.
2. You can then call the function using the SELECT statement like any other SQL statement:

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SELECT sum_numbers(5, 10);

This will return the result of the function call, which in this case is 15.

Note: PostgreSQL supports multiple procedural languages (PL), and plpgsql is one of them. Other options include plpythonu (Python), plperl (Perl), and more. You can choose the language that best suits your requirements when creating the function.