![]() ![]() Each row in the inventory table has one and only one row in the film table. Let’s look at the following film and inventory tables from the sample database.Įach row in the film table may have zero or many rows in the inventorytable. Note that the LEFT JOIN is also referred to as LEFT OUTER JOIN. The following Venn diagram illustrates how the LEFT JOIN clause works: In addition, it fills the columns that come from the right table with NULL. In case these values are not equal, the left join clause also creates a new row that contains columns that appear in the SELECT clause. If these values are equal, the left join clause creates a new row that contains columns that appear in the SELECT clause and adds this row to the result set. For each row in the left table, it compares the value in the pka column with the value of each row in the fka column in the right table. The LEFT JOIN clause starts selecting data from the left table. Third, specify the right table (table B) in the LEFT JOIN clause and the join condition after the ON keyword. ![]() Second, specify the left table (table A) in the FROM clause.First, specify the columns in both tables from which you want to select data in the SELECT clause.To join the table A with the table B table using a left join, you follow these steps: LEFT JOIN B ON pka = fka Code language: SQL (Structured Query Language) ( sql ) The following statement illustrates the LEFT JOIN syntax that joins the table A with the table B : SELECT To select data from the table A that may or may not have corresponding rows in the table B , you use the LEFT JOIN clause. Suppose that you have two tables: A and B.Įach row in the table A may have zero or many corresponding rows in the table B while each row in the table B has one and only one corresponding row in the table A . Introduction to PostgreSQL LEFT JOIN clause Summary: in this tutorial, you will learn how to use the PostgreSQL LEFT JOIN clause to select data from multiple tables.
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