SQLite on iOS...alter table IF?

Question

I have inherited an existing iOS app codebase and have been told to alter a sqlite table but not use versioning (as in not just store a constant somewhere in the app that dictates how/whether to update the table). Is there a way to check whether a column exists and add that column if it doesn't exist without versioning?

Answer 1

Use SQLite's pragma table_info() to get a result set that includes one row per table. For example:

create table foo (bar text, baz text)

and

pragma table_info('foo')

That returns a two row result set:

[cid: 0, pk: 0, notnull: 0, name: bar, type: text, dflt_value: <null>]
[cid: 1, pk: 0, notnull: 0, name: baz, type: text, dflt_value: <null>]

So, perform pragma table_info('table') and then iterate through the rows returned and see if a row with a name value equal to the column you're looking for exists.