If a subquery returns any record, the Exists condition will return a TRUE value, or else, it will return a FALSE.The PostgreSQL EXISTS condition is a type of Boolean operator which returns the true or false result. It is used to group with a subquery and test the existence of records in a subquery. In other words, we can say that the EXISTS condition is used to check for the presence of any data in a subquery, and returns true if the subquery returns several records. In PostgreSQL, the EXISTS condition can combine with the SELECT, INSERT, UPDATE, and DELETE commands. Introduction of PostgreSQL EXISTS Condition And we also see examples of EXISTS Condition with different queries such as INSERT, SELECT, NOT EXISTS, NULL, UPDATE, and DELETE. In this section, we are going to understand the working of PostgreSQL EXISTS Condition, which is used with the WHERE clause to evaluate the existing rows in a subquery. Both methods have their advantages and disadvantages, so choose the one that best suits your needs.Next → ← prev PostgreSQL Exists Condition One way is to use the `INSERT INTO ON CONFLICT DO UPDATE RETURNING` statement, and the other way is to use a function. In conclusion, there are two ways to insert data into a table only if it does not already exist and return the id of the existing row in PostgreSQL. If it does not, we use the `INSERT INTO` statement to insert the values and return the id of the newly inserted row. If it does, we return the id of the existing row. Inside the function, we are using a `SELECT INTO` statement to check if the row already exists. In the above example, we are creating a function called `insert_if_not_exists` that takes in the table name, column values, and returns an integer. INSERT INTO table_name (column1, column2, column3) Here is an example of how to do this: CREATE OR REPLACE FUNCTION insert_if_not_exists(table_name text, column1 text, column2 text, column3 text) Using a FunctionĪnother way to insert data into a table only if it does not already exist and return the id of the existing row is by using a function. Finally, we use the `RETURNING` clause to return the id of the existing row. If it does, we update `column2` to `’new_value’`. In this case, we are checking if `column1` already exists. We are also using the `ON CONFLICT` clause to specify the column that we want to check if it already exists. In the above example, we are inserting values into `table_name` and specifying the columns we want to insert into. ON CONFLICT (column1) DO UPDATE SET column2 = 'new_value' RETURNING id Here is an example of how to use the `INSERT INTO ON CONFLICT DO UPDATE RETURNING` statement: INSERT INTO table_name (column1, column2, column3) If the row already exists, it updates the existing row and returns the id of the existing row. The `INSERT INTO ON CONFLICT DO UPDATE RETURNING` statement in PostgreSQL allows us to insert a new row into a table only if it does not already exist. Using INSERT INTO ON CONFLICT DO UPDATE RETURNING In this guide, we will show you how to insert data into a table only if it does not already exist and return the id of the existing row if it does. However, the problem with this approach is that it does not return the id of the existing row. In such cases, we can use the `INSERT INTO` statement in combination with the `ON CONFLICT DO NOTHING` clause to achieve this. When working with PostgreSQL, it is often necessary to insert data into a table only if it does not already exist. Guide: Insert if not exists, else return id in PostgreSQL
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