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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.
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.
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.
4 Απρ 2021 · DELETE t1 FROM data t1 JOIN data t2 USING (channel_id,timestamp) WHERE t1.id > t2.id
The GROUP BY clause groups rows into summary rows based on column values or expressions. It returns one row for each group and reduces the number of rows in the result set. The GROUP BY clause is an optional part of the SELECT statement.
To return a particular key value (such as the smallest or largest), include a LIMIT clause in the appropriate query. For example: mysql> SELECT JSON_OBJECTAGG(c, i) OVER (ORDER BY i) AS json_object FROM t LIMIT 1; +-----+ | json_object | +-----+ | {"key": 3} | +-----+ mysql> SELECT JSON_OBJECTAGG(c, i) OVER (ORDER BY i DESC) AS json_object FROM ...
