![]() The following example shows how to combine the IF() function with the GROUPING() function to substitute labels for the super-aggregate NULL values in orderYear and productLine columns: SELECT IF( GROUPING(orderYear), We often use GROUPING() function to substitute meaningful labels for super-aggregate NULL values instead of displaying it directly. Similarly, the GROUPING(productLine) returns 1 when NULL in the productLine column occurs in a super-aggregate row, 0 otherwise. The GROUPING(orderYear) returns 1 when NULL in the orderYear column occurs in a super-aggregate row, 0 otherwise. The GROUPING() function can be used in the select list, HAVING clause, and (as of MySQL 8.0.12 ) ORDER BY clause. The GROUPING() function returns 1 when NULL occurs in a supper-aggregate row, otherwise, it returns 0. To check whether NULL in the result set represents the subtotals or grand totals, you use the GROUPING() function. The hierarchy in this example is: orderYear > productLineĬode language: SQL (Structured Query Language) ( sql ) The GROUPING() function The ROLLUP generates the subtotal every time the year changes and the grand total at the end of the result set. If you reverse the hierarchy, for example: SELECT The hierarchy in this case is: productLine > orderYear Code language: SQL (Structured Query Language) ( sql ) The ROLLUP generates the subtotal row every time the product line changes and the grand total at the end of the result. WITH ROLLUP Code language: SQL (Structured Query Language) ( sql ) Then the ROLLUP generates the following grouping sets: (c1, c2) () Code language: SQL (Structured Query Language) ( sql )Īnd in case you have two columns specified in the GROUP BY clause: GROUP BY c1, c2 WITH ROLLUP Code language: SQL (Structured Query Language) ( sql ) The ROLLUP assumes that there is the following hierarchy: c1 > c2 > c3 Code language: SQL (Structured Query Language) ( sql )Īnd it generates the following grouping sets: (c1, c2, c3) If you have more than one column specified in the GROUP BY clause, the ROLLUP clause assumes a hierarchy among the input columns.įor example: GROUP BY c1, c2, c3 WITH ROLLUP Code language: SQL (Structured Query Language) ( sql ) Productline WITH ROLLUP Code language: SQL (Structured Query Language) ( sql )Īs clearly shown in the output, the ROLLUP clause generates not only the subtotals but also the grand total of the order values. The ROLLUP generates multiple grouping sets based on the columns or expressions specified in the GROUP BY clause. The ROLLUP clause is an extension of the GROUP BY clause with the following syntax: SELECT To fix these issues, you can use the ROLLUP clause. The performance of the query may not be good since the database engine has to internally execute two separate queries and combine the result sets into one.This query is able to generate the total order values by product lines and also the grand total row. The NULL in the productLine column identifies the grand total super-aggregate line. ![]() If you want to generate two or more grouping sets together in one query, you may use the UNION ALL operator as follows: SELECTīecause the UNION ALL requires all queries to have the same number of columns, we added NULL in the select list of the second query to fulfill this requirement. Sales Code language: SQL (Structured Query Language) ( sql ) The following query creates an empty grouping set denoted by the (): SELECT SUM(orderValue) totalOrderValue Productline Code language: SQL (Structured Query Language) ( sql ) For example, the following query creates a grouping set denoted by (productline) SELECT The following query returns all rows from the sales table: SELECT * FROM sales Code language: SQL (Structured Query Language) ( sql ) MySQL ROLLUP OverviewĪ grouping set is a set of columns to which you want to group. SUM(quantityOrdered * priceEach) orderValueĬode language: SQL (Structured Query Language) ( sql ) The data comes from the products, orders, and orderDetails tables in the sample database. The following statement creates a new table named sales that stores the order values summarized by product lines and years. Summary: in this tutorial, you will learn how to use the MySQL ROLLUP clause to generate subtotals and grand totals.
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