SQLite-在WHERE NOT EXISTS语句中使用无关联的多个值

Question

EDIT: Answer was that you had to enable foreign keys upon every connection. SQLiteCommand command = new SQLiteCommand("PRAGMA foreign_keys = ON"

I looked all over and didn't see an analogue to my question, so if there is an answer just point me in that direction and I'll move on...

I am trying to make a table that is a relation between two other tables, that stores a value for another table.

Let's say the create statements for the tables are:

CREATE TABLE First ( FirstID Integer PRIMARY KEY, Name Text, otherThing Text)

CREATE TABLE Second ( SecondID Text PRIMARY KEY, OtherStuff VarChar(10) )

CREATE TABLE Third ( FirstID Integer, SecondID Text, SomeData Text, 
     FOREIGN KEY (FirstID) REFERENCES First(FirstID),
     FOREIGN KEY (SecondID) REFERENCES Second(SecondID),
     PRIMARY KEY ( FirstID, SecondID) )

What I want to do is create an insert statement that only allows the insertion into Third when the FirstID is present in First and the SecondID is present in Second.

Any help on what I can try? The syntax I have tried (and failed with) is:

INSERT INTO Third (FirstID, SecondID, SomeData) SELECT 123, "foo", "Interesting Data Here" WHERE EXISTS ( SELECT FirstID FROM First AND SELECT SecondID FROM Second) 

INSERT INTO Third (FirstID, SecondID, SomeData) SELECT 123, "foo", "Interesting Data Here" WHERE EXISTS ( SELECT FirstID FROM First) AND WHERE EXISTS( SELECT SecondID FROM Second)

Answer 1

The foreign key constraints already forbid invalid IDs.

But if you want to silently ignore rows with nonexistent IDs, you have to check manually. Your second query is correct, but it cannot have more than one WHERE clause:

INSERT INTO Third (FirstID, SecondID, SomeData)
SELECT 123, 'foo', 'Interesting Data Here'
WHERE EXISTS (SELECT 1 FROM First  WHERE FirstID  = 123)
  AND EXISTS (SELECT 1 FROM Second WHERE SecondID = 'foo');