How to add column to table? - sqlite

Question

Using "react-native-sqlite-storage" the application is already live on Google Play. I want to add two columns to an existing database table in such a way the application will not crash for existing users.

Answer 1

When you will add column to existing table you will get error like
error: {"message":"no such column: todoStar","code":5} // todoStar is column name
In error block you can alter the table and add your column. Make sure you write the code inside error block
if (error.message.indexOf('no such column: todoStar') > -1) {
dbConnection.transaction(function (tx2) {
let query = 'ALTER TABLE todos ADD todoStar Int(32);'; // todos is tableName
tx2.executeSql(
query,
'',
async (tx3) => {
console.log('new column added');
},
(error) => {
console.error(
'error: while adding column' + JSON.stringify(error),
);
},
);
});
}

Answer 2

As usual official documentation only contains basic information, and there is not much information on migration or database upgrades.
After hours of long research, I found that SQLite has user_version which can be used to know which version the user currently has, based on that we can execute upgrade queries.
I am using expo-sqlite, but the below solution should also work for react-native-sqlite-storage
Example:
/** database.tsx **/
export function getUserDBVersion() {
return new Promise<SQLite.SQLResultSet>((resolve, reject) => {
database.transaction((tx) => {
tx.executeSql(
`PRAGMA user_version`,
[],
(_, res) => {
resolve(res);
},
(_, error) => {
reject(error);
return true;
}
);
});
});
}
export function updateUserDBVersion(version: number) {
return new Promise<SQLite.SQLResultSet>((resolve, reject) => {
database.transaction((tx) => {
tx.executeSql(
`PRAGMA user_version = ?`,
[version],
(_, res) => {
resolve(res);
},
(_, error) => {
reject(error);
return true;
}
);
});
});
}
/** App.tsx **/
useEffect(() => {
getUserDBVersion().then((res) => {
const user_version = res.rows._array[0].user_version;
if (user_version < 1) {
//User has old version
//(1) Run function to upgrade your database tables
alterTables().then(() => {
//(2) Update user_version so that next time you can check if < 2 for new updates
updateUserVersion(1);
});
}
});
}, []);
I think this is an elegant way for 2 reasons
You can update all of your databases and tables in one place
You can display the splash screen until all this migration is completed
*For readability I have not added error handling part above
*Most of the above code will be the same for react-native-sqlite-storage, if not update your code accordingly
*The above code is in typescript, simply remove types if you are using jsx