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9 Ιουν 2011 · delete from YourTable where YourTable.columnA in (select columnA from YourTable group by column A having count(*) > 1)
The GROUP BY statement groups rows that have the same values into summary rows, like "find the number of customers in each country". The GROUP BY statement is often used with aggregate functions ( COUNT() , MAX() , MIN() , SUM() , AVG() ) to group the result-set by one or more columns.
DELETE del FROM words AS del JOIN ( SELECT `char`, category, ( SELECT i.id FROM words AS i WHERE i.`char` = d.`char` AND i.category = d.category ORDER BY i.id DESC LIMIT 1 OFFSET @N ) AS id FROM words AS d GROUP BY `char`, category ) AS tmp ON del.`char` = tmp.`char` AND del.category = tmp.category AND del.id <= tmp.id ;
This MySQL tutorial explains how to use the MySQL GROUP BY clause with syntax and examples. The MySQL GROUP BY clause is used in a SELECT statement to collect data across multiple records and group the results by one or more columns.
This MySQL tutorial explains how to use the MySQL DELETE statement with syntax and examples. Description. The MySQL DELETE statement is used to delete a single record or multiple records from a table in MySQL. Syntax. In its simplest form, the syntax for the DELETE statement in MySQL is: DELETE FROM table. [WHERE conditions];
4 Απρ 2021 · DELETE t1 FROM data t1 JOIN data t2 USING (channel_id,timestamp) WHERE t1.id > t2.id
25 Ιουλ 2024 · In MySQL, the GROUP BY clause is a powerful tool for grouping rows with the same values into summary rows, enabling efficient data analysis. It is often used with aggregate functions like SUM , COUNT , AVG , MIN , and MAX to perform calculations on grouped data.
