What is SQL COALESCE? The SQL COALESCE function is used to handle NULL values in a database query by returning the first non-NULL value from a list of expressions or column values. It allows you to provide a default or fallback value when NULL values are encountered in the data. COALESCE...
The SQL COALESCE function returns the first non-null value in a list. It helps handle null values by substituting with the first non-null alternative. Learn more.
SELECT COALESCE(d.department_id, e.department_id)FROM departments dFULL JOIN employees e ON (e.department_id = d.department_id); 我们已经介绍了许多查询的示例,接下来看看其他的数据操作。 DML DML 表示数据操作语言,也就是插入、更新和删除。以下是一个插入语句示例: CREATE TABLE test(id int); --...
The COALESCE function is used as an alternative to the ISNULL() function or the CASE statement. The advantage over the ISNULL() function is that ISNULL() only take two parameters and COALESCE() can take many parameters. The advantage over a CASE statement is that it is easier of writing...
SQL>SELECTCOALESCE(0.9*list_price, min_price,5)FROMDUAL;---NULLIF(NULL,'5','6',NULL,'9') 返回第一个非空值。 七、条件表达式 case 和 decode SQL>SelectD.Job, Decode(D.Job,'CLERK','c','SALESMAN','S','O'),CaseWhenD.Job='CLERK'Then'C'WhenD.Job='SALESMAN'Then'S'EndAsLieFrom...
selectCOALESCE(null,5,6,null,9) from dual;---返回第一个非空值 select POWER(2.2,2.2) from dual; ---a的b次方 十、一些有用的字符串操作函数: select CHR(95) from dual;---ASCII码对应字符 select ASCII('_') from dual;---字符对应ASCII码 select concat('aa','bb') from...
SELECT emp_name AS "姓名", salary * 12 + COALESCE(bonus, 0) "年薪" FROM employee; 解析:SQL 中的别名可以为查询中的表或结果指定一个临时名称。别名使用关键字 AS 表示,可以省略。 6. 怎么查看女性员工的信息? 答案: SELECT * FROM employee WHERE sex = '女'; 解析:SQL 中使用 WHERE 子句指定过...
sum(CASE WHEN i.object_ID IS NULL THEN0ELSE1END) AS The_Count, coalesce(stuff(( SELECT','+i2.name FROM sys.indexes i2 WHERE t.object_ID=i2.object_ID ORDER BY i2.name FOR XML PATH(''), TYPE).value(N'(./text())[1]',N'varchar(8000)'),1,2,''),'') AS Index_List ...
(n/a)') AS referencing_column, referencing_class_desc, referenced_class_desc, referenced_server_name, referenced_database_name, referenced_schema_name, referenced_entity_name, COALESCE(COL_NAME(referenced_id, referenced_minor_id), '(n/a)') AS referenced_column, is_caller_dependent, is_...
SQL>select lpad('what is this',5),lpad('what is this',25),lpad('what is this',25,'-') from dual; ---用指定的字符串(what is this)从左补齐多少个字符(5个)字符串不够的用-补齐,what is this',5,'-' 1. trim去空格的 replace替换 ...