SQL查看與檢查選項

Question

我目前正在研究意見......但我看到有一個視圖類型「與檢查選項」（transact sql）...我kindda困惑它是做什麼...請小小的幫助

Answer 1

它不是視圖類型，而是視圖選項，它使視圖函數成爲插入/更新操作的約束。
只有當視圖可以檢索到插入的記錄時，才能通過視圖向表中插入記錄或將記錄插入表中。
只有當視圖可以檢索更新的記錄時，才能通過視圖更新表的記錄。

PostgreSQL的演示

create table mytable (i int); 
create view myview as select i from mytable where i <= 10 with check option; 

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insert into myview (i) values (1),(2),(3); 

19:26:00 [INSERT - 3 rows, 0.010 secs] Command processed ... 1 statement(s) executed, 3 rows affected, exec/fetch time: 0.010/0.000 sec [1 successful, 0 errors]

insert into myview (i) values (11); 

19:26:20 [INSERT - 0 rows, 0.000 secs] [Code: 0, SQL State: 44000] ERROR: new row violates check option for view "myview" Detail: Failing row contains (11). ... 1 statement(s) executed, 0 rows affected, exec/fetch time: 0.000/0.000 sec [0 successful, 1 errors]

update myview set i=i*10 where i=1; 

19:27:29 [UPDATE - 1 rows, 0.000 secs] Command processed ... 1 statement(s) executed, 1 rows affected, exec/fetch time: 0.000/0.000 sec [1 successful, 0 errors]

update myview set i=i*10 where i=2; 

19:27:42 [UPDATE - 0 rows, 0.000 secs] [Code: 0, SQL State: 44000] ERROR: new row violates check option for view "myview" Detail: Failing row contains (20). ... 1 statement(s) executed, 0 rows affected, exec/fetch time: 0.000/0.000 sec [0 successful, 1 errors]