In SQL, the NULL value is never true in comparison to any other value, even NULL. An expression that contains NULL always produces a NULL value unless otherwise indicated in the documentation for the operators and functions involved in the expression. All columns in the following example return ...
SQL 复制 > 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 are done -- in a null-safe manner. > SELECT name, age FROM person IN...
As mentioned in the introduction, this guide focuses on how to use SQL’s comparison andIS NULLoperators to filter data. If you’d like to learn how to use theBETWEENorINoperators with range and membership predicates, respectively, we encourage you to check out this guide onHow To Use the ...
如果NOT IN子查询中用到的表里被选择的列中存在NULL,则 SQL 语句整体的查询结果永远是空。 EXISTS谓词永远不会返回unknown。EXISTS只会返回true或者false。 因此就有了IN和EXISTS可以互相替换使用,而NOT IN和NOT EXISTS却不可以互相替换的混乱现象。 4、ALL运算符与null 以下是ALL运算符语法: scalar_expression comp...
In some cases, it is possible to simplify a complex comparison by filtering out null values from a column explicitly - for example when no null values are present or these values are not relevant in the result. Consider the following example:C#...
SQL Server does not pad the two values to the same length before the comparison occurs. Because the purpose of the LIKE predicate, by definition, is to facilitate pattern searches rather than simple string equality tests, this does not violate the section of the ANSI SQL-92 specification mentio...
SQL> insert into test(id, name) values(2, ''); 1 row created. SQL> insert into test(id, name) values(3, ' '); --符号中' '有一个空格 1 row created. SQL> insert into test(id, name) values(4, ' '); --符号中' '有两个空格 ...
Other SQL Tutorial PL/SQL Tutorial SQL Comparison KeywordsThere are other comparison keywords available in sql which are used to enhance the search capabilities of a sql query. They are "IN", "BETWEEN...AND", "IS NULL", "LIKE".Comparision...
Standard Query Operator Translation The "Null Semantics" section of this topic describes null comparison semantics in LINQ to SQL. System.String Methods The "Differences from .NET" section of this topic describes how a return of 0 from LastIndexOf might mean either that the string is null or ...
SELECT CustomerID, AccountNumber, TerritoryID FROM AdventureWorks2008R2.Sales.Customer WHERE TerritoryID IN (1, 2, 3) OR TerritoryID IS NULL Transact-SQL supports an extension that allows for the comparison operators to return TRUE or FALSE when comparing against null values. This option is activ...