![]() INSERT INTO mytable VALUES (1,'one'), (2,'two') For example, you could create and fill a table by writingĬREATE TABLE mytable (id int primary key, data text) In general, any SQL command that does not return rows can be executed within a PL/pgSQL function just by writing the command. Note that this could result in run-time errors generated by the input function, if the string form of the result value is not acceptable to the input function. If no assignment cast is known for the pair of data types involved, the PL/pgSQL interpreter will attempt to convert the result value textually, that is by applying the result type's output function followed by the variable type's input function. If the expression's result data type doesn't match the variable's data type, the value will be coerced as though by an assignment cast (see Section 10.4). Equal ( =) can be used instead of PL/SQL-compliant :=. The target variable can be a simple variable (optionally qualified with a block name), a field of a row or record target, or an element or slice of an array target. The expression must yield a single value (possibly a row value, if the variable is a row or record variable). 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.An assignment of a value to a PL/pgSQL variable is written as: variable expression Īs explained previously, the expression in such a statement is evaluated by means of an SQL SELECT command sent to the main database engine. 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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