![]() In a DELETE, the data available to RETURNING is the content of the deleted row. In an UPDATE, the data available to RETURNING is the new content of the modified row. The RETURNING clause is also very useful with INSERT. INSERT INTO users (firstname, lastname) VALUES ('Joe', 'Cool') RETURNING id For example, when using a serial column to provide unique identifiers, RETURNING can return the ID assigned to a new row:ĬREATE TABLE users (firstname text, lastname text, id serial primary key) But it can be very handy when relying on computed default values. This is not so useful in trivial inserts, since it would just repeat the data provided by the client. In an INSERT, the data available to RETURNING is the row as it was inserted. A common shorthand is RETURNING *, which selects all columns of the target table in order. It can contain column names of the command's target table, or value expressions using those columns. The allowed contents of a RETURNING clause are the same as a SELECT command's output list (see Section 7.3). Use of RETURNING avoids performing an extra database query to collect the data, and is especially valuable when it would otherwise be difficult to identify the modified rows reliably. The INSERT, UPDATE, and DELETE commands all have an optional RETURNING clause that supports this. In this tutorial, you have learned how to use the PostgreSQL UPDATE join statement to update data in a table based on values in another table.Sometimes it is useful to obtain data from modified rows while they are being manipulated. The following SELECT statement retrieves the data of the product table to verify the update: SELECT * FROM product Code language: SQL (Structured Query Language) ( sql )Īs you can see, the net_price column has been updated with the correct values. If there is a match in both tables, it gets the discount from the product_segment table, calculates the net price based on the following formula, and updates the net_price column. This statement joins the product table to the product_segment table. You can utilize the table aliases to make the query shorter like this: UPDATE WHERE gment_id = product_segment.id Code language: SQL (Structured Query Language) ( sql ) To do this, you can apply the UPDATE join statement as follows: UPDATE product Third, suppose you have to calculate the net price of every product based on the discount of the product segment. ( 'nulla elit ac', 161.71, 3) Code language: SQL (Structured Query Language) ( sql ) CREATE TABLE product(įOREIGN KEY(segment_id) REFERENCES product_segment( id) The product table has the foreign key column segment_id that links to the id of the segment table. ![]() Second, create another table named product that stores the product data. For example, products with the grand luxury segment have 5% discount while luxury and mass products have 6% and 10% discounts respectively. The product_segment table has the discount column that stores the discount percentage based on a specific segment. We will use the following database tables for the demonstration:įirst, create a new table called product_segment that stores the product segments including grand luxury, luxury, and mass. Let’s take a look at an example to understand how the PostgreSQL UPDATE join works. If the value in the c2 column of table t1 equals the value in the c2 column of table t2, the UPDATE statement updates the value in the c1 column of the table t1 the new value ( new_value). The FROM clause must appear immediately after the SET clause.įor each row of table t1, the UPDATE statement examines every row of table t2. To join to another table in the UPDATE statement, you specify the joined table in the FROM clause and provide the join condition in the WHERE clause. In this case, you can use the PostgreSQL UPDATE join syntax as follows: UPDATE t1Ĭode language: SQL (Structured Query Language) ( sql ) Sometimes, you need to update data in a table based on values in another table. ![]() Introduction to the PostgreSQL UPDATE join syntax Summary: in this tutorial, you will learn how to use the PostgreSQL UPDATE join syntax to update data in a table based on values in another table.
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