If you want to include NULL values as "not equal" then you need a NULL safe operator. Otherwise, the <> returns NULL , which is treated as " ... ... <看更多>
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If you want to include NULL values as "not equal" then you need a NULL safe operator. Otherwise, the <> returns NULL , which is treated as " ... ... <看更多>
... <看更多>
More Boolean Expressions to Filter SQL Queries – How to filter SQL data using comparison operators, such as "greater than" and "not equal to". ... <看更多>
SQL Standard 92 defines <> as not equals operator , (http://www.contrib.andrew.cmu.edu/~shadow/sql/sql1992.txt ) . Technically, != is an ... ... <看更多>