Scenario 2.a: Delete Duplicate rows but keep one using CTE We need to use the technique of Self Join initially to check for duplicate records containing different custid but same passport number. select distinct a.* from customers2 a join customers2 b on a.custid <> b.custid and a.CustN...
How to Delete the Duplicate Rows Delete key1by Büşra ÖZCOŞKUNCC BY-SA 4.0 Now you've identified the copies, you often want to delete the extra rows. For simplicity, I'm going to assume that either the rows are exact copies or you don't care which you remove. If there is on...
Write a SQL query to delete all duplicate email entries in a table namedPerson, keeping only unique emails based on itssmallestId. +---+---+ | Id | Email | +---+---+ | 1 | john@example.com | | 2 | bob@example.com | | 3 | john@example.com | +---+---+ Id is the ...
The output demonstrates that we have inserted three rows with the same book title by mistake. It is a problem. The simple solution is to remove the unnecessary rows, applying the specific condition for removing rows with duplicate titles. How to Delete Data in SQL Column Based on a Condition...
那如果换成delete呢?同样保持开关打开,跟踪如下:"steps": [ { "expanded_query": "/* select#2 */ select `t_table_2`.`id` from `t_table_2` where (`t_table_2`.`uid` = 1)" }, { "transformation": { "select#": 2, "from": "IN (SELECT)", "to": "semijoin", "chosen": fal...
一种PL/SQl解决方案:使用存储过程删除冗余数据,叫做DeleDuplicate 的存储过程,这个过程的结构很清晰的. SQL Listing 6. The DeleteDuplicate stored procedure 它将这些冗余行选择一到一个游标中,然后从表中取出每一个冗余行来进行与游标中的行进行 比对,然后决定是否删除 ...
当SQL 对 SELECT 语句进行求值时,根据满足 SELECT 语句的搜索条件的行数,可能有几行符合结果表中的条件。 结果表中的某些行可能重复。 您可以使用 DISTINCT 关键字指定不需要任何重复项,后跟表达式列表: SELECT DISTINCTJOB, SEX ... DISTINCT 表示您只想选择唯一行。 如果所选行与结果表中的另一行重复,那么将忽...
"to":"semijoin", "chosen":false } }, { "transformation": { "select#":2, "from":"IN (SELECT)", "to":"EXISTS (CORRELATED SELECT)", "chosen":true, "evaluating_constant_where_conditions": [ ] } } ] "expanded_query":"/* select#1 */ select `t_table_1`.`id` AS `id`,`t_...
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