SQLITE (fmdb) select where x is null not working
fmdb, ios, isnull, sqlite
Solution
`NULL` cannot be compared with the `=` operator; it is not equal with any value, even itself.
To compare with `NULL`, you have to use the `IS NULL` operator:
stmt = @"select * from test where shipToCode is null";
Problem
I'm using FMDB on iOS, attempting to query a table with a statement such as, ``` select * from test where foo isNull ``` In the sqlite C API, this ends up binding to null using this API, ``` int sqlite3_bind_null(sqlite3_stmt*, int); ``` This isn't working. The select invoked through fmdb which seems to be correctly binding the column to null is not finding matching records. If in the sqlite3 command line session I do the following command, it works, but not through the sqlite C API via FMDB. ``` select * from test where foo isNull; ``` Here's fmdb code which reproduces the problem. It looks like fmdb is doing the proper steps invoking sqlite3_bind_null. ``` NSString *stmt = @"select * from test where shipToCode=:foo"; NSDictionary *dict = @{@"foo" : [NSNull null]}; FMResultSet *rs = [db executeQuery:stmt withParameterDictionary:dict]; int count = 0; while ([rs next]) { count++; } NSLog(@"Count %d", count); ```