ALTER TABLE Sqlite: how to check if a column exists before alter the table?

Question

Hello everyone!

I need to execute in python a SQL query that adds a new column, in sqlite3.

The problem is that sometimes it already exists. So previous to executing the query I need to check if the column already exists.

If it does, then I won't execute the query.

Is there a way in sqlite to do that? Or do I have to make it through a try-catch block in python code?

Thanks a lot in advance!

Answer 1

You can get a list of columns for a table via the following statement:

PRAGMA table_info('table_name');

More details on the pragma commands are availabel at the sqlite web site

Answer 2

IMO this

conn = sqlite3.connect(':memory:')
c = conn.cursor()
try:
    c.execute('ALTER TABLE mytable ADD COLUMN newcolumn;')
except:
    pass # handle the error
c.close()

is a better choice than constructing special case queries.

You can wrap the above code in a AddColumn(cursor, table, column) function so you can reuse it,
plus it'll make the code more readable.