1.What is the purpose of using DISTINCT on multiple columns in SQL? DISTINCT on multiple columns eliminates rows where all selected fields are identical, ensuring unique combinations of the specified columns in the result set. 2.How does DISTINCT work with multiple columns? When used with multipl...
Select DISTINCT on One Column with Multiple Columns Returned Do you want to use the DISTINCT keyword on one column and show multiple columns? Perhaps you have multiple rows for an ID and want to show only one row for that ID, but want to show multiple columns? Well, you can do that in...
We can also useSELECT DISTINCTwith multiple columns. For example, -- select rows if the first name and country of a customer is uniqueSELECTDISTINCTcountry, first_nameFROMCustomers; Run Code Here, the command selects rows if combinations ofcountryandfirst_nameare unique. Meaning, the result wil...
2) Using the SQL DISTINCT with multiple columns example To find a list of unique cities and countries from theemployeestable, you can specify thecityandcountrycolumns after theDISTINCToperator as shown in the following query: SELECTDISTINCTcity, countryFROMemployees;Code language:SQL (Structured Query...
SELECT DISTINCT column FROM table_name WHERE [condition]; Here, the WHERE condition is optional. The statement applies both to a single column and multiple columns. The syntax of this statement applied to multiple columns is as follows:
SQL DISTINCT SELECT eliminates duplicate records from the results, return only distinct (different) values. DISTINCT aggregates: COUNT, AVG, MAX, etc. so, it operates on one column and does not support multiple columns Suppose that in a table a column may contain many duplicate values ...
mysql> select distinct tiny_column from big_table limit 2; mysql> -- Returns the unique combinations of values from multiple columns. mysql> select distinct tiny_column, int_column from big_table limit 2; distinct可以和聚合函数(通常是count函数)一同使用,count(disitnct)用于计算出一个列或多个...
SQL_AF_DISTINCTSQL_AF_MAXSQL_AF_MINSQL_AF_SUMSQL-92 入口级别一致性驱动程序将始终按支持返回所有这些选项。 SQL_ALTER_DOMAIN 3.0 SQLUINTEGER 位掩码,枚举数据源支持的 SQL-92 中 ALTER DOMAIN 语句中的子句。 SQL-92 完全兼容级别的驱动程序将始终返回所有位掩码。 返回值为“0”表示 不支持 ALTER ...
error occurs if you try to add a new row with a key value that matches an existing row. If you specify a prefix value for a column in a UNIQUE index, the column values must be unique within the prefix length. A UNIQUE index permits multiple NULL values for columns that can contain ...
SELECT COUNT(DISTINCTname)FROMtable1 若无附加条件,同表格中各行的COUNT相等,所以如要返回row的数量,通常写为: SELECT COUNT(*)FROMtable1 WHERE Specify conditions on columns for the rows to be returned Operators: =, <, >, >=, <=, <>, != ...