In this tutorial, we’ll discuss various methods to efficiently count distinct values, with the appropriate examples. 2. Simple SQL Query for Unique Values Counting unique values in a SQL column is straightforward with theDISTINCTkeyword. Here, let’s see how to effectively count distinct entries ...
short ind;intc1val;EXECSQLCREATETABLET1(c1int,c2int);EXECSQLINSERTt1values(1,2);EXECSQLSELECTc1INTO:c1val:indFROMt1WHEREc2=2; 支持SELECT INTO 二维数组功能 ECOB 支持通过SELECT...INTO将 SQL 查询结果存储到二维数组。 示例语句如下所示:
Identify number of unique values in a column: TypeSELECT COUNT(DISTINCTcolumn name)[Enter]FROMtable name; Number of records matching criteria: TypeSELECT COUNT(*)[Enter]FROMtable name[Enter]WHEREcolumn name<,=,or>number; Thequeryelement, an important part of Structured Query Language, retrieves ...
24、unique:create table 表名称 (列名称1 数据类型 not null unique,列名称2 数据类型,...);约束唯一标识数据库表中的每条记录 25、primary key:用法跟unique一样,区别是每个表可以多个unique,但是只能一个primary key。 26、foreign key:一个表中的foreign key 指向另外一个表的primary key;约束用于预防破坏...
SELECTCategory,COUNT(*)ASTotalProducts,SUM(CASEWHENPrice>100THEN1ELSE0END)ASExpensiveProductsFROM...
In SQL, theCOUNT()function is used to count the number of rows that match a specified condition. The DISTINCT keyword is used to return only distinct (unique) values. When combined, COUNT and DISTINCT can be used to count the number of unique values in a column or a set of columns. ...
select * from log where unique (select projectName from log) 子查询的实际运行方式 一般来说,上述几种子查询,如果是非关联子查询,每一行判定结果都一样,意义不是很大。所以,通常上边的这些子查询都会是关联子查询,这样才会每一行结果不一样。而关联子查询一般会在plan优化阶段,转化为join计算。 子查询是一种...
IN SELECTcolumn_name(s) FROMtable_name WHEREcolumn_nameIN(value1,value2,...);<br> = SELECTcolumn_name(s) FROMtable_name WHEREcolumn_name=value1; 5、between BETWEEN 操作符用于选取介于两个值之间的数据范围内的值。 BETWEEN 操作符选取介于两个值之间的数据范围内的值。这些值可以是数值、文本或者...
平均值：avg最小值：min最大值：max综合：sum计数：count基本聚集select count(*)from course;select count(distinct ID)from teacheswhere semester = 'Spring' and year = 2010;select avg(aalary)from instructorwhere dept_name = 'Comp.Sci.';分组聚集在group by子句中的所有属性上取值相同的元组将被分在...
基本的 MERGE 语句如下: MEGRE INTO target_table [AS t_alias] USING source_table [AS s_alias] ON (condition) WHEN MATCHED THEN UPDATE SET column1 = expr_1, column2 = expr_2, ... WHEN NOT MATCHED THEN INSERT (column1, column2, ...) VALUES (expr_1, expr_2, ...); 其中,target...