postgresql where not null
You would benefit from knowing De Morgan's Law which is fundamental to Boolean logic. In this case, your condition is not what you expressed ..., You can use the "null safe" operator is distinct from instead of <> SELECT * FROM "A" WHERE "B" is distinct from 'C'.
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 postgresql where not null 相關參考資料
PostgreSQL Not-Null Constraint - PostgreSQL Tutorial
To check if a value is NULL or not, you use the Boolean operator IS NULL or IS NOT NULL . The expression NULL = NULL returns NULL. PostgreSQL provides the not-null constraint to enforce a column must... http://www.postgresqltutorial. Postgresql NOT NULL AND <> '' vs NOT NULL OR <> '' - Stack Overflow
You would benefit from knowing De Morgan's Law which is fundamental to Boolean logic. In this case, your condition is not what you expressed ... https://stackoverflow.com postgresql - Not equal and null in Postgres - Stack Overflow
You can use the "null safe" operator is distinct from instead of <> SELECT * FROM "A" WHERE "B" is distinct from 'C'. https://stackoverflow.com sql - Finding columns that are NOT NULL in PostgreSQL - Stack Overflow
COLUMNS WHERE column_name IS NOT NULL ... you just need to know how many columns are nullable and how many are non-nullable? https://stackoverflow.com PostgreSQL: Documentation: 9.5: Comparison Operators
Ordinary comparison operators yield null (signifying "unknown"), not true or false, when either input is null. For example, 7 = NULL yields null, as does 7 ... https://www.postgresql.org PostgreSQL: Documentation: 9.4: Comparison Operators
Ordinary comparison operators yield null (signifying "unknown"), not true or false, when either input is null. For example, 7 = NULL yields null, as does 7 ... https://www.postgresql.org PostgreSQL: Documentation: 8.4: Comparison Operators
Do not write expression = NULL because NULL is not "equal to" NULL. (The null value represents an unknown value, and it is not known whether two unknown ... https://www.postgresql.org PostgreSQL: Documentation: 9.1: Comparison Operators
Ordinary comparison operators yield null (signifying "unknown"), not true or false, when either input is null. For example, 7 = NULL yields null, as does 7 ... https://www.postgresql.org PostgreSQL: IS NOT NULL - TechOnTheNet
https://www.techonthenet.com PostgreSQL: Documentation: 8.3: Comparison Operators
It is highly recommended that these applications be modified to comply with the SQL standard. However, if that cannot be done the transform_null_equals configuration variable is available. If it is en... https://www.postgresql.org |