ALTER TABLE ADD COLUMN IF NOT EXISTS in SQLite

Question

We\'ve recently had the need to add columns to a few of our existing SQLite database tables. This can be done with ALTER TABLE ADD COLUMN. Of course, if the table has alre

Answer 1

You can alternatively use the CASE-WHEN TSQL statement in combination with pragma_table_info to know if a column exists:

select case(CNT) 
    WHEN 0 then printf('not found')
    WHEN 1 then printf('found')
    END
FROM (SELECT COUNT(*) AS CNT FROM pragma_table_info('myTableName') WHERE name='columnToCheck') 

Answer 2

In case you're having this problem in flex/adobe air and find yourself here first, i've found a solution, and have posted it on a related question: ADD COLUMN to sqlite db IF NOT EXISTS - flex/air sqlite?

My comment here: https://stackoverflow.com/a/24928437/2678219

Answer 3

If you are doing this in a DB upgrade statement, perhaps the simplest way is to just catch the exception thrown if you are attempting to add a field that may already exist.

try {
   db.execSQL("ALTER TABLE " + TABLE_NAME + " ADD COLUMN foo TEXT default null");
} catch (SQLiteException ex) {
   Log.w(TAG, "Altering " + TABLE_NAME + ": " + ex.getMessage());
}

Answer 4

I took the answer above in C#/.Net, and rewrote it for Qt/C++, not to much changed, but I wanted to leave it here for anyone in the future looking for a C++'ish' answer.

    bool MainWindow::isColumnExisting(QString &table, QString &columnName){

    QSqlQuery q;

    try {
        if(q.exec("PRAGMA table_info("+ table +")"))
            while (q.next()) {
                QString name = q.value("name").toString();     
                if (columnName.toLower() == name.toLower())
                    return true;
            }

    } catch(exception){
        return false;
    }
    return false;
}

Answer 5

threre is a method of PRAGMA is table_info(table_name), it returns all the information of table.

Here is implementation how to use it for check column exists or not,

    public boolean isColumnExists (String table, String column) {
         boolean isExists = false
         Cursor cursor;
         try {           
            cursor = db.rawQuery("PRAGMA table_info("+ table +")", null);
            if (cursor != null) {
                while (cursor.moveToNext()) {
                    String name = cursor.getString(cursor.getColumnIndex("name"));
                    if (column.equalsIgnoreCase(name)) {
                        isExists = true;
                        break;
                    }
                }
            }

         } finally {
            if (cursor != null && !cursor.isClose()) 
               cursor.close();
         }
         return isExists;
    }

You can also use this query without using loop,

cursor = db.rawQuery("PRAGMA table_info("+ table +") where name = " + column, null);

Answer 6

Here is my solution, but in python (I tried and failed to find any post on the topic related to python):

# modify table for legacy version which did not have leave type and leave time columns of rings3 table.
sql = 'PRAGMA table_info(rings3)' # get table info. returns an array of columns.
result = inquire (sql) # call homemade function to execute the inquiry
if len(result)<= 6: # if there are not enough columns add the leave type and leave time columns
    sql = 'ALTER table rings3 ADD COLUMN leave_type varchar'
    commit(sql) # call homemade function to execute sql
    sql = 'ALTER table rings3 ADD COLUMN leave_time varchar'
    commit(sql)

I used PRAGMA to get the table information. It returns a multidimensional array full of information about columns - one array per column. I count the number of arrays to get the number of columns. If there are not enough columns, then I add the columns using the ALTER TABLE command.