Question

Given:

• an sqlite database with a table T
• the table T contains 10 columns – C0, C1 … C9.
• an sqlite3_stmt pointer corresponding to select C3,C2 from T

OK, so I can fetch the selected column values using the sqlite3_column_XXX family of methods (http://www.sqlite.org/capi3ref.html#sqlite3_column_blob), like this:

sqlite3_stmt *s;
sqlite3_prepare_v2(db, query, sizeof(query), &s, NULL);
while ((result = sqlite3_step(s)) == SQLITE_ROW)
{
  const char *v3 = reinterpret_cast<const char *>(sqlite3_column_text(s, 0);
  const char *v2 = reinterpret_cast<const char *>(sqlite3_column_text(s, 1);
}

What I need is the real index of the selected columns, i.e. 3 for v3 and 2 for v2.

Motivation: I want to be able to parse the returned string value into the real column type. Indeed, my schema says that c3 is a datetime, which sqlite treats as TEXT. So, sqlite3_column_type(s, 0) returns SQLITE3_TEXT, but the table metadata (available from pragma table_info(T)) retains the string datetime, which is the intended type of the column. Knowing it, I can parse the returned string into the respective unix time since the epoch, for instance.

But how can I map the query column index to the table column index:

• query column 0 -> table column 3
• query column 1 -> table column 2

Thanks.

Answer 1

You could use the sqlite C function sqlite3_column_decltype to get the declared column data type from the result stmt? It doesn’t specifically answer your question (getting the original column’s index), but could be an alternative way to achieve what you need?