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PODoes SQLite really not preserve data integrity of foreign key constraints by default?
 

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  1. PODoes SQLite really not preserve data integrity of foreign key constraints by default?
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    <p>Newer versions of SQLite <a href="https://stackoverflow.com/questions/3297363/implement-use-foreign-keys-in-sqlite">support foreign key constraints</a>. It is possible to define </p> <pre><code>CREATE TABLE MASTER (_ID INTEGER PRIMARY KEY, ...); CREATE TABLE SERVANT (_ID INTEGER PRIMARY KEY, MASTERID INTEGER, FOREIGN KEY(MASTERID) REFERENCES MASTER(_ID); </code></pre> <p>According to the documentation by default "NO ACTION" is used for ON DELETE and ON UPDATE. But contrary to other DBS "NO ACTION" seems not to mean, that delete or update is not performed. It seems to mean that nothing is done to preserve integrity, at least according to my tests(*) and if I understand the <a href="http://www.sqlite.org/foreignkeys.html#fk_actions" rel="nofollow noreferrer">documentation</a> right: </p> <blockquote> <p>Configuring "NO ACTION" means just that: when a parent key is modified or deleted from the database, no special action is taken.</p> </blockquote> <p>Thus</p> <pre><code>INSERT INTO MASTER (_ID) VALUES (1); INSERT INTO SERVANT (_ID, MASTERID) VALUES (1,1); DELETE FROM MASTER; </code></pre> <p>gives me an empty MASTER table and a SERVANT table with a foreign key pointing into nowhere.</p> <p>Can anyone confirm this behaviour and maybe explain why it is implemented that way? Or do I have to configure something to make foreign key support work? I am new to SQLite development, so please foregive me, if this is a stupid question.</p> <p><strong>Edit:</strong> (*) my tests were flawed, see <a href="https://stackoverflow.com/questions/17551429/does-sqlite-really-not-preserve-data-integrity-of-foreign-key-constraints-by-def/17601506#17601506">my answer below</a>.</p>
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    1. COI can't answer your specific question, but I've found the SQLite docs to be better than average in terms of accuracy and precision (though often finding the bit of information you're looking for is a challenge).
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