在Java应用中,可以通过JDBC执行SQL查询并使用DISTINCT关键字。例如,以下代码片段展示了如何在Java中使用DISTINCT关键字查询数据库: packagecn.juwatech.database;importjava.sql.Connection;importjava.sql.DriverManager;importjava.sql.ResultSet;importjava.sql
Example: SELECT -- select all countries from the Customers tableSELECTcountryFROMCustomers; This SQL command will return all country entries, including duplicates, from theCustomerstable. To learn more, visitSQL SELECT. Challenge: Write an SQL query to filter out all the duplicate entries. Suppose ...
Use the DISTINCT keyword before the column names in an SQL statement to prevent duplicate rows from being selected. Examples The following example lists only the unique divisions that exist in the Q.ORG table: This query: SELECT DISTINCT DIVISION FROM Q.ORG Produces this report: DIVISION --- ...
The following example query shows how to use the Distinct function with a named set, as well as how to use it with the Count function to find the number of distinct tuples in a set:WITH SET MySet AS{[Customer].[Customer Geography].[Country].&[Australia],[Customer].[Customer Geography...
二、优化之前的sql长这样 是不是挺恐怖的;(此处为了脱敏,我把相关的sql关键词都给打码掉了) 这个sql的执行步骤如下: 1、查询出来d表中的某个id字段包含多个id值的所有的数据(因为此表是1-n的关系,所以需要去重,仅需要拿到不重复的id才可以继续下一个步骤);可以看到此步骤我把查询出来的多个值的结果给生成的...
QueryDsl是一个用于构建类型安全的SQL查询的Java库。它提供了一种流畅的API,使得在Java代码中编写SQL查询变得更加简单和可读性更高。QueryDsl可以与各种关系型数据库进行集成,包括MySQL、PostgreSQL、Oracle等。 在使用QueryDsl进行distinct查询时,如果查询速度较慢,可能有以下几个原因: ...
Based on MySQL 8.0 community version Aggregator_distinct 指聚合型DISTINCT,下面为一些example: ~~~ SQL SELECT COUNT(DISTINCT) 除了COUNT外,MySQL目前agg DISTINTCT只支持数值类
在我提交了代码的时候,架构师给我指出我这个sql这样写会有问题。因为在分库分表的时候,是不支持子查询的。 所以需要把多表的子查询的sql结构进行优化。 二、优化之前的sql长这样 是不是挺恐怖的;(此处为了脱敏,我把相关的sql关键词都给打码掉了)
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Additional Example SELECT * FROM ( SELECT id, name, price, ROW_NUMBER() OVER (PARTITION BY category ORDER BY price DESC) as rn FROM products ) subquery WHERE rn = 1; Powered By This query retrieves the product with the highest price within each category, demonstrating another way to ...