Dynamic SQL in PostgreSQL

1. Introduction

Dynamic SQL is a powerful feature in PostgreSQL that allows for the execution of SQL statements that can be constructed at runtime. This capability is particularly useful for applications that require flexible queries based on user input or other dynamic conditions.

2. Definition

Dynamic SQL refers to SQL statements that are generated and executed at runtime. This is opposed to static SQL, which is predefined and cannot change during execution. Dynamic SQL allows for greater flexibility and can be used to construct complex queries.

3. Usage

In PostgreSQL, dynamic SQL can be executed using the EXECUTE command within a PL/pgSQL function or a DO block. It allows developers to build SQL queries based on variable inputs.

4. Examples

4.1 Simple Dynamic SQL Example

CREATE OR REPLACE FUNCTION dynamic_query(table_name text) RETURNS void AS $$
            DECLARE
                sql text;
            BEGIN
                sql := 'SELECT * FROM ' || quote_ident(table_name);
                EXECUTE sql;
            END;
            $$ LANGUAGE plpgsql;

4.2 Using Parameters in Dynamic SQL

CREATE OR REPLACE FUNCTION dynamic_query_with_param(table_name text, column_name text) RETURNS void AS $$
            DECLARE
                sql text;
            BEGIN
                sql := 'SELECT ' || quote_ident(column_name) || ' FROM ' || quote_ident(table_name);
                EXECUTE sql;
            END;
            $$ LANGUAGE plpgsql;

5. Best Practices

6. FAQ