It turned out that many entries in the table 1 and table 2 had string_field column with NULL values. I thought that JOIN would keep records with NULL values because NULL is equal to NULL, isn’t it? Then I tried: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 SELECTNULL=NULL It ...
</isNotNull> 即使你在bean中不设置id的值，id的初始值也是0而不是null;所以这样配置a.id会等于0 而你把name变量用isNotNull这样配置，name如果不设置值，初始就是null,name的条件不就添加在sql中；isEqual相当于equals，数字用得多些，一般都是判断状态值 <isEqual property="state"compareValue="...
Suppose we wish to retrieve the name of customers whose “last_name” is not equal to null. We can use the query as shown in the following to accomplish this: select * from customer c where last_name is not null; In this case, the query returns all the rows from the customer table ...
= (equals) ,<> (does not equal),!= (does not equal),> (is greater than),>= (is greater than or equal to),< (is less than),<= (is less than or equal to) - 比较条件。 可用于数字比较或字符串排序顺序比较。 对于数值比较,空字符串值(")被计算为0。 在任何相等比较中,NULL总是返...
注意:因between 的范围是个闭区间(greater than or equal to low value and less than or equal to high value .), 故严格意义上应该再减去一个趋于0的小数,这里暂且设置成减去1秒(1/(24*60*60)),如果不要求这么精确的话,可以略掉这步。 七、对where语句的法则 ...
isEqual判断是否相等 isNull判断是否为Null值，就是没有传值（连空格都没有传）
在上述查询中,NULLIF函数将检查column2的值,如果为零,则返回NULL。这样,即使column2为零,查询也不会抛出ORA-01476错误。 方法三:使用CASE语句处理被除数为零 另一种处理ORA-01476错误的方法是使用CASE语句。您可以使用CASE语句在被除数为零时返回特定的值,而不是抛出错误。以下示例演示了如何使用CASE语句...
IsNull c# //判断是否为空,不为空为后面参数值SqlFunc.IsNull<TResult>(TResult thisValue, TResult ifNullValue)//判断是否为空,返回boolSqlFunc.IsNullOrEmpty(object thisValue) GreaterThan c# //大于SqlFunc.GreaterThan(object thisValue, object gtValue)//大于等于SqlFunc.GreaterThanOrEqual(object this...
Understand how SQL NULLIF compares two values and returns NULL if they are equal. Learn syntax and examples for using NULLIF in SQL queries.
這表示比較數據列時,兩個 NULL 值會被視為相等,與一般 EqualTo(=) 運算符不同。範例SQL 複製 > CREATE VIEW unknown_age AS SELECT * FROM person WHERE age IS NULL; -- Only common rows between two legs of `INTERSECT` are in the -- result set. The comparison between columns of the row ...