Question

For kicks I’m writing a “schema documentation” tool that generates a description of the tables and relationships in a database. I’m currently shimming it to work with SQLite.

I’ve managed to extract the names of all the tables in a SQLite database via a query on the sqlite_master table. For each table name, I then fire off a simple

select * from <table name>

query, then use the sqlite3_column_count() and sqlite3_column_name() APIs to collect the column names, which I further feed to sqlite3_table_column_metadata() to get additional info. Simple enough, right?

The problem is that it only works for tables that are not empty. That is, the sqlite_column_*() APIs are only valid if sqlite_step() has returned SQLITE_ROW, which is not the case for empty tables.

So the question is, how can I discover column names for empty tables? Or, more generally, is there a better way to get this type of schema info in SQLite?

I feel like there must be another hidden sqlite_xxx table lurking somewhere containing this info, but so far have not been able to find it.

Answer 1

sqlite> .header on
sqlite> .mode column
sqlite> create table ABC(A TEXT, B VARCHAR);
sqlite> pragma table_info(ABC);
cid         name        type        notnull     dflt_value  pk
----------  ----------  ----------  ----------  ----------  ----------
0           A           TEXT        0                       0
1           B           VARCHAR     0                       0