Luckily, SQL makes selecting multiple columns from a table easy. To select multiple columns from a table, simply separate the column names with commas! Selecting specific columns For example, this query selects two columns, name and birthdate, from the people table: SELECT name, birthdate FROM...
COUNT() function and SELECT with DISTINCT on multiple columns You can use the count() function in a select statement with distinct on multiple columns to count the distinct rows. Here is an example: SELECT COUNT(*) -- Count the number of rows in the result set FROM ( SELECT DISTINCT age...
SELECTID , Name , (SELECTMAX(LastUpdateDate)FROM(VALUES( UpdateByApp1Date), ( UpdateByApp2Date), ( UpdateByApp3Date) )ASUpdateDate ( LastUpdateDate ) )ASLastUpdateDateFROM##TestTable 方法二 SELECTID ,[Name],MAX(UpdateDate)ASLastUpdateDateFROM##TestTable UNPIVOT ( UpdateDateFORDateValIN(...
...在为表设置主键时有以下几种办法: 1.在Columns选项卡中,直接选中主键列的P列复选框,这是最简单的方式。...2.选中一个列,然后单击工具栏中的“属性”按钮,系统将弹出列属性窗口,在该窗口中可以设置该列的各种属性,当然也包括该列是否是否是主键。另外还有一个很重要的复选框是“Identity”。...选中...
name列相同的话,是无法得出name分组之后的最大值,这里要注意一下 转载自:https://www.mssqltips.com/sqlservertip/4067/find-max-value-from-multiple-columns-in-a-sql-server-table/ 三届微软SQL Server MVP MySQL 8.0 OCP 人工智能专业硕士 中国DBA联盟(ACDU)成员 数据库交流QQ群:740052625...
SELECTCOUNT(*)FROMstudentsWHEREage<18; SUM函数 SUM函数用于计算某一列中值的总和,只能用于数值类型的列。其基本语法如下: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 SELECTSUM(column_name)FROMtable_nameWHEREcondition; 例如,从sales表中计算销售额的总和: ...
microsoftml.select_columns(cols: [list, str], **kargs) 说明 选择一组要重新定型的列,删除所有其他列。 参数 cols 要保留的字符串或变量名称列表。 kargs 发送到计算引擎的其他参数。 返回 一个定义转换的对象。 请参阅 concat,drop_columns.
I need to search multiple (3 total) columns for 5 different data types, to return the records being investigated. I tried this using an "OR" statement in the where clause and have had inconsistant results. The first two or statement function perfectly the third works as long as the value...
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...
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 ...