在上述排查分析中,我们得到这个 bug 是由于使用了semi-join的DuplicateWeedout执行策略导致了问题的发生,如果在短时间内无法升级变更数据库,而又想尽量避免这个问题的发生。 一方面肯定是业务侧避免该 SQL 的执行,从 DBA 的角度上考虑的是该 SQL 怎样才能正常执行,那么经过验证: 以下三种解决方案均可解决当前 select ...
SQL > SQL Commands > Distinct In SQL, the DISTINCT keyword is used in the SELECT statement to retrieve unique values from a database table. Any value that has a duplicate will only show up once. SyntaxSELECT DISTINCT "column_name"FROM "table_name";...
3.通常insert操作是不加锁的,但如果在插入或更新记录时,检查到 duplicate key(或者有一个被标记删除的duplicate key),对于普通的insert/update,会加S锁,而对于类似replace into或者insert … on duplicate 这样的SQL语句加的是X锁。 4.insert … select 插入数据时,会对 select 的表上扫描到的数据加S锁; 5....
The following example usesDISTINCTto prevent the retrieval of duplicate titles. SQL USEAdventureWorks2022; GOSELECTDISTINCTJobTitleFROMHumanResources.EmployeeORDERBYJobTitle; GO D. Create tables with SELECT INTO The following first example creates a temporary table named#Bicyclesintempdb. ...
Removes all duplicate rows from the SELECT result so one row is kept from each group of duplicates. ON ( expression [, ...] ) is only reserved for the first row among all the rows with the same result calculated using given expressions. DISTINCT ON expression is explained with the same ...
SQL Fundamentals || Oracle SQL语言 Capabilities of theSELECTStatement(SELECT语句的功能) Data retrieval from data base is done through appropriate and efficient use of SQL. Three concepts from relational theory encompass the capability of the SELECT statement: projection, selection, and joining. ...
DUPLICATE和开启Merge-on-Write的UNIQUE表模型支持任意列建倒排索引。但是AGGREGATE和未开启Merge-on-Write的UNIQU模型仅支持Key列建倒排索引,非Key列不能建倒排索引,这是因为这两个模型需要读取所有数据后做合并,因此不能利用索引做提前过滤。 创建索引 创建索引有两种方式,在建表的同时创建索引和为已存在表的某个字...
To learn more, visitSQL SELECT. Write an SQL query to filter out all the duplicate entries. Suppose you have a table namedListings. The schema of this table is as follows: Listings While job hunting, you notice duplicate entries in your job search platform. ...
CREATE TABLE `dt` ( `id` int(11) NOT NULL, `name` varchar(50) NULL, `score` int(11) NULL ) ENGINE=OLAP DUPLICATE KEY(`id`) DISTRIBUTED BY HASH(`id`) BUCKETS 1; 使用JDBC方式 当您使用JDBCINSERT INTO VALUES方式写入时,为了减少SQL解析和生成规划的开销,云数据库 SelectDB 版支持了MySQL协...
SQL Server : duplicate selectYour union query is doing the required duplication, what you need is...