The database engine typically sorts the result set based on the specified columns and then eliminates duplicate rows to produce the final distinct result set. Check out our 1000+ SQL Exercises with solution and explanation to improve your skills. ...
,可以使用DISTINCT关键字来实现。DISTINCT关键字用于返回唯一不重复的结果集。 在SQL中,可以使用SELECT语句来查询数据。如果查询结果中存在几乎重复的行,可以通过在SELECT语句...
SELECT...FROM <tab> UPTO<n> ROWS... WHERE语句: 1.where条件语句 SELECT...WHERE <s> <opertor> <f> ... 2.常用语句 SELECT...WHERE <s> [NOT]BETWEEN<f1>AND<F2>.SELECT...WHERE COL2LIKE'_ABC%'.SELECT...WHERE <s> [NOT]IN(<f1>,..,<fn>)...SELECT...WHERE <s> [NOT]IN<se...
Whereas, a regularSELECTstatement without theDISTINCTkeyword retrieves all rows from the specified columns, including duplicate values. Let's look at an example. Example: SELECT DISTINCT -- select distinct countries from the Customers tableSELECTDISTINCTcountryFROMCustomers; This command will return each...
开始我们拿sql到数据库查询平台查库执行计划,无奈这个平台有bug,delete语句无法查看,所以我们改成select,“应该”是一样。这个“应该”加了双引号,导致我们走了一点弯路。 EXPLAINSELECT*fromt_table_1wheretask_idin(selectidfromt_table_2whereuid=1)
Excludeduplicaterowsinqueryresults. NotethateachSELECTclausecanonlybeusedonce,DISTINCT. TOPnExpr[PERCENT] Inallrecordsthatconformtothequerycondition,selecta specifiednumberorpercentageofrecords.TheTOPclausemust beusedinconjunctionwiththeORDERBYclause.TheORDERBY ...
SQL Server 2014 Enterprise - duplicate (do not use)SQL Server 2017 Enterprise on Windows 症状 请考虑以下情况: 在分区表上创建聚集列存储索引。 如果存在可变长度列,则表中的列的最大长度大于表的8060字节行限制。 使用大容量插入...
For the complete syntax, see SELECT - SQL Command. The detailed syntax for the UNION clause is as follows: 复制 [UNION [ALL] SELECTCommand] Parameters [UNION [ALL] SELECTCommand] Specifies another SELECT statement. By default, UNION eliminates duplicate rows from the combined result set. 备注...
Following the SELECT keyword, you can use a number of modifiers that affect the operation of the statement. HIGH_PRIORITY, STRAIGHT_JOIN, and modifiers beginning with SQL_ are MySQL extensions to standard SQL. The ALL and DISTINCT modifiers specify whether duplicate rows should be returned. ALL ...
ALL prevents UNION from eliminating duplicate rows from the combined results. UNION clauses follow these rules: You cannot use UNION to combine subqueries. Both SELECT commands must have the same number of columns in their query output. Each column in the query results of one SELECT must have ...