iPhone, sqlite3, how do I pass values into a select statement? - iphone

Question

This is the code I'm using to select some records from my database. I'm binding two dates into my sql, however, when I get to sqlite3_step I get SQLITE_DONE where I should be getting SQLITE_ROW. It looks like its processing the bindings rather than querying the data.
What am I doing wrong ?
NSString *startDateRangeString = #"2000-05-01";
NSString *endDateRangeString = #"2011-05-01";
sqlite3 *database;
int result = sqlite3_open("mydb.db", &database);
if(result != SQLITE_OK)
{
NSLog(#"Could not open db.");
}
const char *sql = "select pid from tmp where due >= '%#' and due < '%#' order by due, pid;";
sqlite3_stmt *statementTMP;
int error_code = sqlite3_prepare_v2(database, sql, -1, &statementTMP, NULL);
if(error_code == SQLITE_OK) {
sqlite3_bind_text(statementTMP, 1, [startDateRangeString UTF8String], -1, SQLITE_TRANSIENT);
sqlite3_bind_text(statementTMP, 2, [endDateRangeString UTF8String], -1, SQLITE_TRANSIENT);
int step_error_code = sqlite3_step(statementTMP);
while(sqlite3_step(statementTMP) == SQLITE_ROW) // I get 101 aka SQLITE_DONE
{
NSLog(#"Found!!");
}
}
sqlite3_finalize(statementTMP);
sqlite3_close(database);

Answer 1

I think your SQL is bad. Instead of %# you should use ? for the positional parameters.
I strongly suggest using a wrapper to simplify life. FMDB is a great one at http://github.com/ccgus/fmdb.

Answer 2

char *statementTMP = "select pid from tmp where due >= '?1' and due < '?2' order by due, pid";
....
sqlite3_bind_text(statementTMP, 1, [startDateRangeString UTF8String], -1, SQLITE_TRANSIENT);
sqlite3_bind_text(statementTMP, 2, [endDateRangeString UTF8String], -1, SQLITE_TRANSIENT);

Answer 3

This is by design.
sqlite3_step returns SQLITE_ROW for each row in the resultset, and SQLITE_DONE to indicate there are no more rows. So if a resultset contains N rows, then N calls would return SQLITE_ROW and (N+1)st returns SQLITE_DONE. An empty resultset is not in any way special, it follows the same logic with N=0 (so the very first call returns SQLITE_DONE). This allows client code to handle all resultsets uniformly.
Hope that helps.
Let me know if you need anymore help.
PK

Answer 4

If I read correctly.. You are not executing the statement.. you are just preparing.. you have to do both..
this part just prepare the query
if (sqlite3_prepare_v2(database, sql, -1, &stmt, NULL) != SQLITE_OK)
{
NSLog(#"SQL Warning: failed to prepare statement
with message '%s'.", sqlite3_errmsg(database));
}
This part actually executes the query
if(sqlite3_exec(database, sql, nil, &stmt, &errmsg) == SQLITE_OK)
{
NSLog(#"it means that you query executed correctly");
if(sqlite3_step(stmt) == SQLITE_ROW)
{
NSLog(#"Found!!");
}
}else
{
NSLog(#"SQL Warning: '%s'.", sqlite3_errmsg(database));
}
=)