IF函数 -if(cond,then_return,else_return) mysql> select if('ABC'>'aBC','+++','---'); +---+ | if('ABC'>'aBC','+++','---') | +---+ | --- | +---+ 1 row in set (0.00 sec) 1. 2. 3. 4. 5. 6. 7. 表达式下推 当TiDB从TiKV中读取数据的时候,TiDB会尽量下推一...
SELECTCASEWHENdenominator=0THENNULLELSEnumerator/denominatorENDASResultFROMYourTable; 1. 2. 3. 4. 5. 6. 在这个例子中,我们检查除数denominator是否为0,如果是,则返回NULL,否则进行除法运算。 3. 使用NULLIF函数 NULLIF函数是处理除数为零的一种简洁方法。它的使用方式是,如果两个参数相等,则返回NULL,否则返回...
postgres=# CREATE OR REPLACE PROCEDURE pro_if_then(IN i INT) postgres-# AS postgres$# BEGIN postgres$# IF i>5 AND i<10 THEN postgres$# dbms_output.put_line('This is if test.'); postgres$# ELSEIF i>10 AND i<15 THEN postgres$# dbms_output.put_line('This is elseif test.'); ...
IF(value,t,f) 如果value是true t 如果是false 返回值f select sname,IF(age>40,'中年','青年') as age from s ifnull(value1,value2) 如果value1不为空,返回value1,如果value1为空,返回value2 select sname,IFNULL(email,'没有邮箱') as 邮箱 from s Case when value1 then result1 else default...
CASE Statement when not null , else if Help Case statement with Between in Where Clause Case statement with Date Comparison CASE statement with substring CASE WHEN - Adding collate into it. Case WHEN and concatenate string CASE WHEN isnumeric(ColValue) THEN ... ELSE ... END CASE WHEN MIN,...
NULL、! NULL 資料欄或欄位內容 ! IN 以及!BETWEEN,必須取代為:CREATE ... IF NOT EXISTS、IS NOT NULL、NOT NULL 資料欄或欄位內容 NOT IN 和NOT BETWEEN。 這項變更可確保一致性、符合 SQL 標準,並讓您的 SQL 更具可攜性。 布林值前綴運算子 !(例如 !is_mgr 或!(true AND false))不受這項變更...
Therefore, even if the column has more than 200 unique values, the histogram might have fewer than 200 steps. For a column consisting of only unique values, then the consolidated histogram will have a minimum of three steps.Напомена If the histogram has been built using a sample ...
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if @x > @y print ‘x > y’ –打印字符串’x > y’ else if @y > @z print ‘y > z’ else print ‘z > y’ –CASE use pangu update employee set e_wage = case when job_level = ‟1‟ then e_wage*1.08 when job_level = ‟2‟ then e_wage*1.07 when job_level = ...
The DIR_PATH_NAME and DIR_OBJ_NAME values cannot be NULL (or blanks). If the DIR_TYPE value is DCE, then the DIR_PATH_NAME value must start with either of the special DCE strings enclosed in the following quotes: "/.../" or "/.:/". ...