为了更好的进行null值的比较,在SQL:1999中引入了 IS DISTINCT FROM,在SQL:2003中引入了它的反义,IS NOT DISTINCT FROM。 a IS DISTINCT FROM b可以重写为: ((a <> b OR a IS NULL OR b IS NULL) AND NOT (a IS NULL AND b IS NULL)) a IS NOT DISTINCT FROM b可以重写为: (NOT (a <> ...
SQL:1999中引入了 IS DISTINCT FROM，用于更好地比较null值。在SQL:2003中，引入了IS NOT DISTINCT FROM作为其反义词。a IS DISTINCT FROM b 可以被重写为a IS NOT DISTINCT FROM b。理解这个概念，可以借助下表：使用表来直观展示比较逻辑，有助于更清晰地理解。尽管MySQL并未实现IS DISTINCT FROM和...
I'm reading over a query that performs a left outer join on itself with several on clauses. One of the on clauses is like so: gl1.COLUMN1ISNOTDISTINCTFROMgl2.COLUMN1 How is this different from saying ongl1.COLUMN1=gl2.COLUMN1 IS NOT DISTINCT FROM will also return true if gl1.COL...
SQL的is [not] distinct from是“=”和“is”的混合。常规的“=”遇到NULL时,会返回NULL。is [not] distinct from 则把NULL当作一种数据类型进行处理。 当两个NULL比较时,NULL is not distinct from NULL 返回true,NULL is distinct from NULL返回false。 'a' is distinct from null 或者null is distinct ...
IS [NOT] DISTINCT FROM 谓词 IS [NOT] DISTINCT FROM谓词是比较两个表达式的便捷方式,即使在涉及NULL值时也能确保结果为 true 或 false。 谓词用于WHERE和HAVING子句的搜索条件中,还用于FROM子句的联接条件以及需要布尔值的其他构造中。 在SQL Server 中使用NULL值可能具有挑战性,因为比较它们会导致结...
IS [NOT] DISTINCT FROM 这一谓词用于 WHERE 子句和 HAVING 子句的搜索条件中,还用于 FROM子句的联接条件以及需要布尔值的其他构造中。Transact-SQL 语法约定语法syntaxsql 复制 expression IS [NOT] DISTINCT FROM expression 参数expression任何有效的表达式。
从积极的方面来说，我认为Postgres会为is distinct from使用一个索引，我不认为索引一定会用于所有的替代...
For Hyperscale SLA, seeSLA for Azure SQL Database. Buffer pool, resilient buffer pool extension, and continuous priming In Azure Database Hyperscale, there is a distinct separation between compute and storage. Storage contains all the database pages in one database, and can be allocated over mu...
Databricks SQL Databricks Runtime 测试参数是否具有不同的值,其中 NULL 被视为可比较值。 语法 expr1 is [not] distinct from expr2 参数 expr1:可比较类型的表达式。 expr2:一种表达式类型,该表达式与expr1共有最不常见类型。 返回 一个布尔值。
What is difference between unique and distinct in SQL? The main difference between Unique and Distinct in SQL is thatUnique helps to ensure that all the values in a column are differentwhile Distinct helps to remove all the duplicate records when retrieving the records from a table. ...