if we add a NOT NULL constraint to a table column, we enforce a rule that a value MUST be provided for that column. This can, in turn, help prevent the errors that occur from NULL values and preserve the
在mysql中： select eid,ent_name from ent_search where enttype_code is NULL; 在elasticsearch中，...
您的触发器函数在BEFORE触发器中是正确的，因为它修改了您要插入的行。但在INSTEAD OF触发器中则不正确...
在postgres中，可以使用DROP NOT NULL:
此要求是Cloud Spanner PostgreSQL的特定要求，也是与开源PostgreSQL的偏差（参见“Spanner与开源PostgreSQL的...
(null)的结果将始终为null。要与null进行比较，需要is [not] null或is [not] distinct from null ...
更新时，找到位置直接更新 2.唯一性索引 查找时，遇到第一个符合条件的直接返回。 更新时，先查找...
I get the following error: PostgresError: null value in column "id" of relation "pairs" violates not-null constraint What confuses me is that in Directus, I have checked 'ON CREATE: Generate and Save UUID,' which is working just fine. Please help me understand how I can get around thi...
I am on Postgres 12 (via psycopg) on SQLAlchemy 1.4.15, but I don't think this is too relevant. I want to create the expression NOT (x IS NULL), but I always get x IS NOT NULL. Example code (even without DB connection, so not Postgres-specific): import sqlalchemy as sa t =...
如上面Postgres SQL查询语句，如果IN / NOT IN括号内的条件存在null值，会导致查询失败，因此如果括号内有通过SELECT获得的值作为条件，应当排除查询结果为null的值。