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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.
If the query does not use GROUP BY (which usually imposes its own ordering regardless) and you prefer a particular key ordering, you can invoke JSON_OBJECTAGG() as a window function by including an OVER clause with an ORDER BY specification to impose a particular order on frame rows.
2 Μαρ 2018 · MySQL Delete with Group By and Having clauses. To achieve this exploit with a single simple MySQL command, we are using two useful functions: 1. GROUP_CONCAT () This function returns a string result with the concatenated non-NULL values from a group. It returns NULL if there are no non-NULL values. 2.
4 Απρ 2021 · DELETE t1 FROM data t1 JOIN data t2 USING (channel_id,timestamp) WHERE t1.id > t2.id
DELETE is a DML statement that removes rows from a table. A DELETE statement can start with a WITH clause to define common table expressions accessible within the DELETE. See Section 15.2.20, “WITH (Common Table Expressions)” . Single-Table Syntax. DELETE [LOW_PRIORITY] [QUICK] [IGNORE] FROM tbl_name [[AS] tbl_alias]
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.
