php - 检查SQL约束值

Question

是否可以检查现有约束的特定值？

例如，我想检查 FOREIGN KEY 约束是否为 ON DELETE SET NULL 或 ON DELETE NO ACTION。

我仅在存在约束的情况下找到解决方案，而不是针对特定值。

Answer 1

对于 Postgres 来说，这将是这样的:

select tc.table_schema||'.'||tc.table_name as referencing_table, 
       ctu.table_schema||'.'||ctu.table_name as referenced_table_name,
       rc.update_rule, 
       rc.delete_rule
from information_schema.table_constraints tc
  join information_schema.referential_constraints rc 
    on tc.constraint_catalog = rc.constraint_catalog 
   and tc.constraint_schema = rc.constraint_schema 
   and tc.constraint_name = rc.constraint_name
  join information_schema.constraint_table_usage ctu 
    on ctu.constraint_catalog = rc.unique_constraint_catalog
   and ctu.constraint_schema = rc.unique_constraint_schema
   and ctu.constraint_name = rc.unique_constraint_name
where tc.table_name = 'foobar'
  and tc.table_schema = 'public'
  and tc.constraint_type = 'FOREIGN KEY'

但这在 MySQL 上不起作用