[英]How to merge two sqlite databases without losing foreign keys?
我正在開發用於使用flutter
和sqflite
軟件包學習外語的移動應用程序。 該應用程序具有sqlite
數據庫,其中包含單詞表和某種類型的集合(多對多關系)。 此數據存儲在應用程序資產中,並在安裝應用程序時像在sqflite指南https://github.com/tekartik/sqflite/blob/master/sqflite/doc/opening_asset_db.md中一樣加載到移動數據庫目錄中
用戶可以添加自己的單詞和集合,也可以添加或更改我的單詞。 我曾經以為我可以使用sqlite upsert
實現此目的,但是如果用戶添加的單詞與我在應用程序更新中添加的單詞相同,則會出現沖突。 如果我進行upsert
則該單詞不會出現在我的單詞集中,因為它們受id約束;否則,如果我執行replace
,則單詞將從用戶的集合中消失。
我想我需要在sqlite insert or replace
某種級聯ID更新,但是沒有這種功能。
有什么想法嗎?
我認為我需要在sqlite插入或替換中進行某種級聯ID更新,但是沒有這種功能。
有這樣的功能; 您可以將ON UPDATE CASCADE
指定為FOREIGN KEY定義/條款的一部分。 您還可以編碼ON DELETE CASCADE
SQLite外鍵支持-4.3。 ON DELETE和ON UPDATE操作 。
由於這被編碼為子表的一部分,因此您不能使用ALTER TABLE COLUMN更改列的屬性(除了重命名列之外)。 你不得不 :-
INSERT INTO replacement_table_with_original_name SELECT * FROM renamed_table
(明顯改變replacement_table_with_original_name和renamed_table)實際名稱。 例如,考慮場景的以下表示形式(從可用信息中得出),這將在保留現有數據的同時添加ON UPDATE CASCADE
和ON DELETE CASCADE
,它另外刪除無沖突的行,並且還更新引用的值而無沖突或丟失:-
-- Create the original tables and load some test data
CREATE TABLE IF NOT EXISTS word_table (id INTEGER PRIMARY KEY, other_column TEXT);
INSERT INTO word_table VALUES (null,'WA'),(null,'WB'),(null,'WC');
CREATE TABLE IF NOT EXISTS collection_table (id INTEGER PRIMARY KEY, other_column TEXT);
INSERT INTO collection_table VALUES (null,'CA'),(null,'CB'),(null,'CC');
CREATE TABLE IF NOT EXISTS word_collection_map (
word_reference INTEGER NOT NULL REFERENCES word_table(id),
collection_reference INTEGER NOT NULL REFERENCES collection_table(id),
PRIMARY KEY (word_reference,collection_reference) ) WITHOUT ROWID;
INSERT INTO word_collection_map VALUES(1,1),(3,2),(3,3),(2,1),(2,2),(2,3);
-- show the result
SELECT word_table.other_column, collection_table.other_column
FROM word_collection_map
JOIN word_table ON word_table.id = word_reference
JOIN collection_table ON collection_table.id = collection_reference
;
-- ADDING CASCADE
ALTER TABLE word_collection_map RENAME TO old_word_collection_map;
CREATE TABLE IF NOT EXISTS word_collection_map (
word_reference INTEGER NOT NULL REFERENCES word_table(id) ON UPDATE CASCADE ON DELETE CASCADE ,
collection_reference INTEGER NOT NULL REFERENCES collection_table(id) ON UPDATE CASCADE ON DELETE CASCADE,
PRIMARY KEY (word_reference,collection_reference) ) WITHOUT ROWID;
INSERT INTO word_collection_map SELECT * FROM old_word_collection_map;
DROP TABLE IF EXISTS old_word_collection_map;
-- Show results (should match first)
SELECT word_table.other_column, collection_table.other_column
FROM word_collection_map
JOIN word_table ON word_table.id = word_reference
JOIN collection_table ON collection_table.id = collection_reference
;
-- DELETE a word no conflicts
DELETE FROM word_table WHERE other_column = 'WC';
SELECT word_table.other_column, collection_table.other_column
FROM word_collection_map
JOIN word_table ON word_table.id = word_reference
JOIN collection_table ON collection_table.id = collection_reference
;
-- UPDATE the FK parent no conflicts
UPDATE collection_table SET id = 10 WHERE id = 3;
SELECT word_table.other_column, collection_table.other_column
FROM word_collection_map
JOIN word_table ON word_table.id = word_reference
JOIN collection_table ON collection_table.id = collection_reference
;
-- Create the original tables and load some test data
CREATE TABLE IF NOT EXISTS word_table (id INTEGER PRIMARY KEY, other_column TEXT)
> OK
> Time: 0.118s
INSERT INTO word_table VALUES (null,'WA'),(null,'WB'),(null,'WC')
> Affected rows: 3
> Time: 0.104s
CREATE TABLE IF NOT EXISTS collection_table (id INTEGER PRIMARY KEY, other_column TEXT)
> OK
> Time: 0.097s
INSERT INTO collection_table VALUES (null,'CA'),(null,'CB'),(null,'CC')
> Affected rows: 3
> Time: 0.094s
CREATE TABLE IF NOT EXISTS word_collection_map (
word_reference INTEGER NOT NULL REFERENCES word_table(id),
collection_reference INTEGER NOT NULL REFERENCES collection_table(id),
PRIMARY KEY (word_reference,collection_reference) ) WITHOUT ROWID
> OK
> Time: 0.097s
INSERT INTO word_collection_map VALUES(1,1),(3,2),(3,3),(2,1),(2,2),(2,3)
> Affected rows: 6
> Time: 0.105s
-- show the result
SELECT word_table.other_column, collection_table.other_column
FROM word_collection_map
JOIN word_table ON word_table.id = word_reference
JOIN collection_table ON collection_table.id = collection_reference
> OK
> Time: 0.001s
-- ADDING CASCADE
ALTER TABLE word_collection_map RENAME TO old_word_collection_map
> OK
> Time: 0.108s
CREATE TABLE IF NOT EXISTS word_collection_map (
word_reference INTEGER NOT NULL REFERENCES word_table(id) ON UPDATE CASCADE ON DELETE CASCADE ,
collection_reference INTEGER NOT NULL REFERENCES collection_table(id) ON UPDATE CASCADE ON DELETE CASCADE,
PRIMARY KEY (word_reference,collection_reference) ) WITHOUT ROWID
> OK
> Time: 0.096s
INSERT INTO word_collection_map SELECT * FROM old_word_collection_map
> Affected rows: 6
> Time: 0.094s
DROP TABLE IF EXISTS old_word_collection_map
> OK
> Time: 0.081s
-- Show results (should match first)
SELECT word_table.other_column, collection_table.other_column
FROM word_collection_map
JOIN word_table ON word_table.id = word_reference
JOIN collection_table ON collection_table.id = collection_reference
> OK
> Time: 0s
-- DELETE a word no conflicts
DELETE FROM word_table WHERE other_column = 'WC'
> Affected rows: 1
> Time: 0.086s
SELECT word_table.other_column, collection_table.other_column
FROM word_collection_map
JOIN word_table ON word_table.id = word_reference
JOIN collection_table ON collection_table.id = collection_reference
> OK
> Time: 0.001s
-- UPDATE the FK parent no conflicts
UPDATE collection_table SET id = 10 WHERE id = 3
> Affected rows: 1
> Time: 0.089s
SELECT word_table.other_column, collection_table.other_column
FROM word_collection_map
JOIN word_table ON word_table.id = word_reference
JOIN collection_table ON collection_table.id = collection_reference
> OK
> Time: 0s
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