百度试题 题目SQL 语句可返回唯一不同的值的是( )。 A. SELECT ALL B. SELECT DIFFERENT C. SELECT UNIQUE D. SELECT DISTINCT 相关知识点: 试题来源: 解析 D null 反馈 收藏
A UNIQUE index creates a constraint such that all values in the index must be distinct. An 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 ...
(50), C3 DATETIME); GO CREATE UNIQUE INDEX AK_Index ON #Test (C2) WITH (IGNORE_DUP_KEY = ON); GO INSERT INTO #Test VALUES (N'OC', N'Ounces', GETDATE()); INSERT INTO #Test SELECT * FROM Production.UnitMeasure; GO SELECT COUNT(*) AS [Number of rows] FROM #Test; GO DROP ...
select A,B,C.. from xx; SELECT title,release_year,country FROM films; select all 选择数据库里全部的列 SELECT*FROM films; SELECT DISTINCT often your results will include many duplicate values. If you want to select all the unique values from a column, you can use the DISTINCT keyword. SE...
SELECT column1, column2 FROM：查询表中的特定列。SELECT name, email FROM users;条件查询 WHERE：有...
百度试题 结果1 题目使用sql数据进行查询操作时若希望查询结果不出现重复元组,应在select语句中使用( ) A. UNIQUE B. ALL C. EXCEPT D. DISTINCT 相关知识点: 试题来源: 解析 D 反馈 收藏
For example, you can create constraints on a column to disallow null values or provide a default value if a value is not specified, or you can assign a key constraint on the table that enforces uniqueness or defines a relationship between tables. The data in the table can be compressed ...
-- 显示employees和departments表中UNIQUE的部门编号。SELECTdepartment_idFROMemployeesUNIONSELECTdepartment_...
get the unique values in one column of a table select distinct job from emp; WHERE, return the specific info where some cases satisfied. SELECT* FROM EMP WHERE job = 'MANAGER' /*if 'maneger', no data found,这里“=”后面的值需要注意大小写* ...
SELECTSUM(column_name)FROMtable_nameWHERECONDITIONGROUPBYcolumn_nameHAVING(arithematicfunctioncondition); SQL CREATE TABLE 语句 CREATETABLEtable_name( column1 datatype, column2 datatype, column3 datatype, ... columnN datatype, PRIMARYKEY( oneormorecolumns) );...