1. IF-ELSE语句的语法 在MySQL中,IF-ELSE语句的基本语法如下所示: IF condition THEN statement1; statement2; ... ELSE statement3; statement4; ... END IF; 1. 2. 3. 4. 5. 6. 7. 8. 9. 其中,condition是一个布尔表达式,如果为真(即非零),则执行statement1,statement2等等;如果为假(即零),...
则执行相应的 statement(s)。如果 condition 为假，则跳过该条件并检查下一个 ELSE IF 条件，如果没有...
CREATE PROCEDURE cusBycon AS IF (SELECT COUNT(*) FROM Customers WHERE Country = "France") == 0 BEGIN IF (SELECT COUNT(*) FROM Customers WHERE Country = "Germany") = 0 BEGIN SELECT * FROM Customers WHERE Country = "Australia" as Country END ELSE BEGIN SELECT * FROM Customers WHERE Coun...
使用case声明：
是为了方便拼接后面符合条件的 if 标签语句块,否则没有 1=1 的话我们拼接的 SQL 就会变成 select * from user where and age > 0 , 显然这不是我们期望的结果,当然也不符合 SQL 的语法,数据库也不可能执行成功,所以我们投机取巧添加了 1=1 这个语句,但是始终觉得多余且没必要,Mybatis 也考虑到了,所以等...
IF STATEMENT WITH A CASE STATEMENT WITHIN A SQL SELECT if there's any errors stop running the remaining of the script possible? IFNULL replacement function Ignore error row when update or insert ms sql server ignore first row of data file in bulk insert Ignore milliseconds on SELECT query?
How can i left join both id_branch and id_supplier to display qty? Currently it will only show the product from id_branch even select the product from id_supplier. If i am changing the left join to //PisproducttableLEFTJOINtableCASCONC.id_supplier=P.id_supplierORC.id_branch=P.id...
statement block end 1. 2. 3. 2.if...else语句:该语句用来定义有条件执行的某些语句。 if boolen_expression statement [else [if boolean_expression] statement] 1. 2. 3. 示例:查询学号为9704学生的成绩状况 if ( select min (mark) from student where sno= '9704') > 90 print...
if-then-else -- 单分支:如果条件成立则执行SQL1,否则执行SQL2if conditions then-- SQLend if;-- 案例create procedure proc_test13(in a int)begin if a=1 then insert into classes(class_name,class_remark) values('go','test'); end if;end;-- 双分支:如果条件成立则执行SQL1,否则执行SQL2if...
IF Boolean_expression { sql_statement | statement_block } [ ELSE { sql_statement | statement_block } ] 参数说明: Boolean_expression返回True或False的表达式。如果布尔表达式包含SELECT语句,则SELECT语句必须用括号括起来 { sql_statement | statement_block }使用语句块定义的任何有效的Transact-SQL语句...