然后我们观察到t2.date总是在case语句的两种情况下进行比较,即non-null。我们可以用下面的coalesce语句来表示case-statement: t2.date = coalesce(t1.date, t3date) 它看起来干净多了,但在功能上仍然与case语句相同。 请注意,如果您没有从t2和t3投射任何值,那么进行where date in (select date from t2) or...
The case statement in SQL returns a value on a specified condition. We can use a Case statement in select queries along with Where, Order By, and Group By clause. It can be used in the Insert statement as well. In this article, we would explore the CASE statement and its various use...
PreparedStatement 是Java编程语言中的一个接口,用于执行预编译的SQL语句。它继承自 Statement 接口,允许在执行SQL查询之前将参数添加到SQL语句中。...此外,它允许参数化查询,即将动态值作为参数传递到SQL语句中,防止了SQL注入攻击的风险。...防止 SQL 注入攻击: 通过参数化查询,PreparedStatement 允许将参数传递到 SQL...
-- multiple CASE conditions in SQLSELECTcustomer_id, first_name,CASEWHENcountry ='USA'THEN'United States of America'WHENcountry ='UK'THEN'United Kingdom'ENDAScountry_nameFROMCustomers; Run Code Here, the result set contains a new column,country_namealong withcustomer_idandfirst_name. The value...
Let’s illustrate with an example. The following SQL statement will return “Monday” if today is a Monday, otherwise it returns “Not a Monday”. SETDATEFIRST1-- first day of the week is a MondaySELECTCASEWHENDATEPART(WEEKDAY,GETDATE())=1THEN'Monday'ELSE'Not a Monday'END ...
SQL USEAdventureWorks2022; GOSELECTProductNumber,Category=CASEProductLineWHEN'R'THEN'Road'WHEN'M'THEN'Mountain'WHEN'T'THEN'Touring'WHEN'S'THEN'Other sale items'ELSE'Not for sale'END,NameFROMProduction.ProductORDERBYProductNumber; GO B. Use a SELECT statement with a searched CASE expression ...
CASE 语句在指定的搜索条件为 true 时执行一条或多条语句。 CASE 是独立的语句,它与必须作为表达式组成部分出现的 CASE 表达式不同。 CASE 语句有两种形式:简单 CASE 语句和搜索型 CASE 语句。 简单CASE 语句 (PL/SQL) 简单CASE 语句尝试将表达式 (称为选择器) 与一个或多个 WHEN 子句中指定的另一个表达式...
SQL USEAdventureWorks2022; GOSELECTProductNumber,Category=CASEProductLineWHEN'R'THEN'Road'WHEN'M'THEN'Mountain'WHEN'T'THEN'Touring'WHEN'S'THEN'Other sale items'ELSE'Not for sale'END,NameFROMProduction.ProductORDERBYProductNumber; GO B. Use a SELECT statement with a searched CASE expression ...
SQL---CASE WHEN条件表达式(conditional statement) CASE表达式是用来判断条件的,条件成立时返回某个值,条件不成立时返回另一个值。 语法: CASEWHENComparsionConditionTHENresultWHENComparsionConditionTHENresultELSEotherEND (注:各分支返回的数据类型需一致。)...
Simple Case Statement CASE [input_expression] WHEN when_expression THEN when_true_result_expression [...n] [ELSE else_result_expression] END Search Case Statement CASE WHEN Boolean_expression THEN when_true_result_expression [...n] [ELSE else_result_expression] END ...