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
I executed the above SQL statements to display the inserted data in the below image. Here we can see there are duplicate rows in the table in column Name and City. Now, let’s run the SQL SELECT UNIQUE statement on this table to display its output. I have executed SQL SELECT UNIQUE st...
If the data is expected to have duplicate results, use DISTINCT keyword to eliminate duplicates and diplay only the unique results in the query output. Only the selected columns are validated for duplication and the rows will be logically eliminated from the query output. To be noted, the DISTI...
NOT NULL:指示某列不能存储 NULL 值。 UNIQUE:确保某列的值都是唯一的。 PRIMARY Key:NOT NULL 和 UNIQUE 的结合。确保某列(或两个列多个列的结合)有唯一标识,有助于更容易更快速地找到表中的一个特定的记录。。 FOREIGN Key: 保证一个表中的数据匹配另一个表中的值的参照完整性。 CHECK: 保证列中的值...
【题目】关于SQL,用unique,这道题错在哪里?提示unique附近有语法错误找出只教授一门课程的老师的姓名*select PNAMEfrom PROFwhere unique(select PNOfrom PCwhere PC.PNO=PROF.PNO)就看这个错在哪里哦?不再写其他的 答案 【解析】select pnamefrom prof p1,pc p2where p1.pno=p2.pnogroup by pnamehavi...
The SELECT statement in SQL is used to retrieve data from a relational database. SyntaxNumber of ColumnsSQL Syntax 1 SELECT "column_name" FROM "table_name"; More Than 1 SELECT "column_name1"[, "column_name2"] FROM "table_name"; All SELECT * FROM "table_name";"...
Specify a comment that passes instructions to the optimizer on choosing an execution plan for the statement. See Also: "Hints "andOracle Database Performance Tuning Guidefor the syntax and description of hints DISTINCT | UNIQUE SpecifyDISTINCTorUNIQUEif you want the database to return only one co...
Once the SQL code complete extension is installed into one or more hosts, it will suppress Microsoft’s native IntelliSense and take over the code completion. Enough talk, let’s open up a new query and see it in action. Start with a simple SELECT statement in SQL Server that you’re ...
You will learn about the COUNT function later in this tutorial.Exercise? Which of the following SQL statements would return a list of all unique countries from a table named 'Customers'? SELECT UNIQUE Country FROM Customers; SELECT Country FROM Customers; SELECT DISTINCT Country FROM Customers; ...
【题目】关于SQL,用unique,这道题错在哪里?【题目】关于SQL,用unique,这道题错在哪里? 相关知识点: 试题来源: 解析 【解析】select pname 【解析】select pname 【解析】select pname 【解析】select pname 【解析】select pname 【解析】select pname ...