Application of Case-when in MySQL LIU Lei1,LIN Li-dan 2 (1.He nan Police College,Zhengzhou 450000, China;2.Luo he Vocational Technology College, Luohe 462000, China) Abstract: In the actual research and development work, it is often necessary to write all kinds of SQL to statistic all ...
CASE WHEN 常用在 SELECT 语句中,可 以根据一定的逻辑判断和判定条件,对不同的值进行返回。接下来, 我们就来详细地了解一下 MySQL 中的 CASE WHEN 的使用方法。 1、基本语法 CASE WHEN 判定条件 1 THEN 输出值 1 WHEN 判定条件 2 THEN 输出值 2 ... ELSE 输出值 N END 当 CASE 后面带的条件不满足时...
It creates plans that will always work. That’s (one of the reasons) why in the first example it was an index scan, not an index seek. 参考这里,可以简单地理解成这种写法,语义上支持不了索引的Seek,最多支持到index scan 至于(@p_CustomerId is null or CustomerId = @p_CustomerId )这种写法...
在这个语句中When Null这一行总是返回unknown,所以永远不会出现Wrong的情况。因为这句可以替换成WHEN col_1 = NULL,这是一个错误的用法,这个时候我们应该选择用WHEN col_1 IS NULL。 === Example: select borrow_min_fund as borrowMinFund, borrow_max_fund as borrowMaxFund, CASE WHEN base_rate_unit=...
when can double the result with half the effort and solve more extensive and logically more compact problems. This paper introduces the business requirements, and then gives the implementation scheme, and then provides the example code, finally summarizes the application scenario.Key words:MySQL; ...
Hi all, I have the below code using case when. I'd like to modify this though so that instead of the code using 1 for true it counts the distinct number of records that match the criteria in each case when section. If someone could please give me some example code?
MySQL 存储过程是一种预编译的 SQL 代码块,可以通过调用执行。CASE语句在存储过程中用于条件判断,类似于编程语言中的if-else结构。以下是CASE语句在MySQL存储过程中的基本写法: 代码语言:txt 复制 DELIMITER // CREATE PROCEDURE example_case_procedure(IN input INT) BEGIN DECLARE result VARCHAR(255); CASE input...
The CASE statement will execute the ELSE clause if none of the WHEN clauses were executed. Example Let's look at an example that shows how to use the CASE statement in MySQL. First, we'll look at the first syntax for the CASE statement. For example: ...
In case none of the when_expression in the WHEN clause matches the value of the case_expression, the commands in the ELSE clause will execute. The ELSE clause is optional. If you omit the ELSE clause and no match found, MySQL will raise an error. The following example illustrates how to...
This bug was fixed in MySQL 8.0.1 with the following commit message: Bug#22887227: ASSERTION FAILED: THIS_TYPE != JSON_DOM::J_ERROR Problem: Item_func_case::val_json() did not always set the null_value flag when the CASE expression evaluated to NULL. Fix: Update Item_func_case's nu...