这表明索引是可以被使用到的。所以PostgreSQL尽管不支持IN谓词等价重写技术,但是索引还是能利用上的。 这时,有另外一个朋友给出解释: 如果那个情况发生了,证明你得做vacuum了,你的数据库表的统计值不对,导致pg的优化器做出了错误的判断。 这个问题的原因,是不是这样的呢?为了进一步定位问题,给出如下建议: 1. name...
As you can see from the output, the DELETE USING query deletes the languages with low IDs and retains the languages with high IDs. If you want the languages with high ids instead of low ids then use the “>” sign in the WHERE clause: DELETE FROM programming_languages dup_lang USING p...
The RETURNING clause is optional which will return a list of all deleted rows or values of the specified column. After the DELETE statement is executed successfully, PostgreSQL will give the message as DELETE count where the count is the number of rows deleted by the DELETE statement. ...
The following syntax shows how to find duplicates in Postgres via theCOUNT()function: SELECT col_name, COUNT(col_name) FROM tab_name GROUP BY col_name HAVING COUNT(col_name)> 1; The above query will count if the selected column has some duplicates or not. Removing Duplicates To remove du...
如果你想做upsert，你必须用唯一约束upsert。所以有两个唯一约束。主键（id），（group_id，item_id）...
如果你想做upsert，你必须用唯一约束upsert。所以有两个唯一约束。主键（id），（group_id，item_id）...
1. Inner join with PostgreSQL DELETE JOIN. DELETEFROMtable_name1WHEREcondition column_nameIN(SELECTtable_name1.idFROMtable_name1INNERJOINtable_name2ONtable_name1.column_name=table_name2.column_nameWHERE[condition] 2. FULL join with PostgreSQL DELETE JOIN. ...
Note: If you wish to check duplicates in thesagecolumn, replace it with thesnamecolumn in the query. In addition, if you wish to find a duplicate record with the same name and age, add both columns to the query. Query 2 If you are well versed with nested queries, this might be an ...
Provided by: postgresql-client-9.3_9.3.24-0ubuntu0.14.04_amd64 NAME DELETE - delete rows of a table SYNOPSIS [ WITH [ RECURSIVE ] with_query [, ...] ] DELETE FROM [ ONLY ] table_name [ * ] [ [ AS ] alias ] [ USING using_list ] [ WHERE condition | WHERE CURRENT OF curso...
Example of PostgreSQL DELETE with WHERE clause The below command is used to delete the rows whose value in thedept_idcolumn is 6: DELETEFROMdepartment WHEREdept_id = 6; After executing the above command, it will return a message withDELETE 1, which implies that one row has been deleted fr...