Updated
Introduction
The ROLLUP operator in MySQL is used with the GROUP BY clause. It is used to create subtotals and grand totals in the result set.
The ROLLUP operator generates a result set that is similar to the one generated by the GROUP BY clause, but with additional rows that represent subtotals and grand totals. The added rows are generated by successively reducing the GROUP BY clause one column at a time, creating subtotals at each step. This can be very useful for generating reports that contain subtotals and totals. The syntax for the use of the ROLLUP is thus:
SELECT
column1, column2,...
FROM
table_name
GROUP BY
column1,
column2,
column2 WITH ROLLUPThe GROUP BY clause in SQL is used to group rows that have the same values in specified columns into aggregated data. The WITH ROLLUP option is used to create subtotals and grand totals within the grouped result set.
SELECT column1, column2,...: This part of the query is selecting the columns that you want to include in your result set.FROM table_name: This part of the query specifies the table from which to retrieve the data.GROUP BY column1, column2, column3 WITH ROLLUP: This part of the query groups the selected columns, creating a separate row for each group of unique values.- The
WITH ROLLUPmodifier causes MySQL to include extra rows that represent the subtotals (which are produced by grouping oncolumn1andcolumn2, andcolumn1,column2andcolumn3) and the grand total (which is produced by grouping on all of the selected columns).
GROUPING() function in the SELECT statement can be used to distinguish super-aggregate rows from regular grouped rows. GROUPING(column) returns 1 for super-aggregate rows and 0 for regular grouped rows.Note: The order of columns in the GROUP BY clause matters when using WITH ROLLUP. The subtotals and grand totals are generated from right to left.
EXAMPLE 1: ROLLUP
EXAMPLE 2: ROLLUP
The GROUPING() function
Study Questions
Test your understanding of ROLLUP and GROUPING concepts:
StudyQuestion 1: ROLLUP Basics
StudyQuestion 2: Hierarchy Understanding
StudyQuestion 3: GROUPING Function
StudyQuestion 4: Practical Application
StudyQuestion 5: Order Impact
ROLLUP & GROUPING Practice Questions
Complete Solutions to Practice Questions
Remember: ROLLUP is powerful for creating summary reports with multiple aggregation levels in a single query. Master the hierarchy concept and you'll unlock comprehensive business analytics! 📊