GROUP BY DATE(payment_date) Code language: SQL (Structured Query Language) ( sql ) To group payments by dates, you use the DATE() function to convert timestamps to dates first and then group payments by the result date: SELECT DATE(payment_date) paid_date, 6) Using PostgreSQL GROUP BY clause with a date column For each group of (customer_id, staff_id), the SUM() calculates the total amount. In this example, the GROUP BY clause divides the rows in the payment table by the values in the customer_id and staff_id columns. The following example uses multiple columns in the GROUP BY clause: SELECT 5) Using PostgreSQL GROUP BY with multiple columns For each group, it returns the number of rows by using the COUNT() function. The GROUP BY clause divides the rows in the payment into groups and groups them by value in the staff_id column. Staff_id Code language: SQL (Structured Query Language) ( sql ) To find the number of payment transactions that each staff has processed, you group the rows in the payment table by the values in the staff_id column and use the COUNT() function to get the number of transactions: SELECT ORDER BY amount DESC Code language: JavaScript ( javascript ) 4) Using PostgreSQL GROUP BY with COUNT() function example SELECTįirst_name || ' ' || last_name full_name, Unlike the previous example, this query joins the payment table with the customer table and group customers by their names. The following statement uses the GROUP BY clause with the INNER JOIN clause the get the total amount paid by each customer. ORDER BY SUM (amount) DESC Code language: SQL (Structured Query Language) ( sql ) 3) Using PostgreSQL GROUP BY clause with the JOIN clause The following statement uses the ORDER BY clause with GROUP BY clause to sort the groups: SELECT Whenever the customer_id changes, it adds the row to the returned result set. The GROUP BY clause sorts the result set by customer id and adds up the amount that belongs to the same customer. The following query uses the GROUP BY clause to get the total amount that each customer has been paid: SELECT For each group, you calculate the total amounts using the SUM() function. The GROUP BY clause is useful when it is used in conjunction with an aggregate function.įor example, to select the total amount that each customer has been paid, you use the GROUP BY clause to divide the rows in the payment table into groups grouped by customer id. 2) Using PostgreSQL GROUP BY with SUM() function example In this case, the GROUP BY works like the DISTINCT clause that removes duplicate rows from the result set. SELECTĬustomer_id Code language: SQL (Structured Query Language) ( sql ) The following query gets data from the payment table and groups the result by customer id. You can use the GROUP BY clause without applying an aggregate function. 1) Using PostgreSQL GROUP BY without an aggregate function example Let’s take a look at the payment table in the sample database. PostgreSQL evaluates the GROUP BY clause after the FROM and WHERE clauses and before the HAVING SELECT, DISTINCT, ORDER BYand LIMIT clauses. It’s possible to use other clauses of the SELECT statement with the GROUP BY clause. The statement clause divides the rows by the values of the columns specified in the GROUP BY clause and calculates a value for each group. Second, list the columns that you want to group in the GROUP BY clause.First, select the columns that you want to group e.g., column1 and column2, and column that you want to apply an aggregate function ( column3).The following statement illustrates the basic syntax of the GROUP BY clause: SELECTĬode language: SQL (Structured Query Language) ( sql ) For each group, you can apply an aggregate function e.g., SUM() to calculate the sum of items or COUNT() to get the number of items in the groups. The GROUP BY clause divides the rows returned from the SELECT statement into groups. Introduction to PostgreSQL GROUP BY clause Summary: in this tutorial, you will learn how to divide rows into groups by using the PostgreSQL GROUP BY clause.
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