FMDB sqlite的SQL查询无法正常工作

Question

I am creating a temp table using the following SQL query. But its not showing any results (result set is empty) when I execute it programmatically, and shows records when I execute it manually on the database.

NSString *query=[NSString stringWithFormat:@"create temp table search2 as select  Observationsid from Observations where admin_id=%d AND teacher_id=%d AND observation_type=%d AND isvalid='yes' AND date BETWEEN '12-20-2013' AND '12-23-2013'",appDelegate.admin_id,appDelegate.teacher_id,appDelegate.observationType];
FMResultSet *results=[appDelegate.database executeQuery:query];

Nslogged query: Printing description of results->_query:

create temp table search2 as select Observationsid from Observations where admin_id=2 AND teacher_id=1 AND observation_type=2 AND isvalid='yes' AND date BETWEEN '12-20-2013' AND '12-23-2013'

and records are there in database.

Answer 1

This SQL statement shouldn't return results, so you should use executeUpdate method rather than a executeQuery method. You should not see any results from this. If you want to see the results, do a separate executeQuery statement returning the results from search2 . (I assume you're building the search2 table for a reason.)

NSString *query=[NSString stringWithFormat:@"create temp table search2 as select  Observationsid from Observations where admin_id=%d AND teacher_id=%d AND observation_type=%d AND isvalid='yes' AND date BETWEEN '12-20-2013' AND '12-23-2013'",appDelegate.admin_id,appDelegate.teacher_id,appDelegate.observationType];
if (![appDelegate.database executeUpdate:query])
    NSLog(@"create error: %@", [appDelegate.database lastErrorMessage]);

query = @"SELECT * FROM search2";
FMResultSet *results = [appDelegate.database executeQuery:query];
if (!results)
    NSLog(@"create error: %@", [appDelegate.database lastErrorMessage]);

---

By the way, while you can get away with stringWithFormat for this particular SQL, that's not a good idea. You generally want to use the ? placeholders, eg

NSString *query = @"create temp table search2 as select  Observationsid from Observations where admin_id=? AND teacher_id=? AND observation_type=? AND isvalid='yes' AND date BETWEEN '12-20-2013' AND '12-23-2013'";
if (![appDelegate.database executeUpdate:query, @(appDelegate.admin_id), @(appDelegate.teacher_id), @(appDelegate.observationType)])
    NSLog(@"create error: %@", [appDelegate.database lastErrorMessage]);

---

Unrelated, but I notice that you're using MM-DD-YYYY format text string for your dates. That's not going to work. SQLite doesn't natively "understand" dates. Notably, if you've stored your dates in MM-DD-YYYY format, a text string of 12-21-2052 is BETWEEN '12-20-2013' AND '12-23-2013' (because text strings are compared in alphabetically order), which is probably not what you intended. See Date And Time Functions .

But, fortunately, FMDB does the NSDate conversion for you, storing it as numeric value. So, for example, let's assume your table was defined as follows:

CREATE TABLE IF NOT EXISTS Observations
    (Observationsid   INTEGER PRIMARY KEY AUTOINCREMENT, 
     admin_id         INTEGER, 
     teacher_id       INTEGER,
     observation_type INTEGER,
     isvalid          TEXT,
     date             REAL);

You really want to use YYYY-MM-DD or, better, rely upon FMDatabase to convert your NSDate values for you. Remember, SQLite does not have proper date formats, so choose an appropriate format (eg YYYY-MM-DD format) or let FMDatabase handle this for you, using NSDate objects.

If you want to facilitate the conversion of date strings to dates, you can use a NSDateFormatter , eg:

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
formatter.dateFormat = @"MM-dd-yyyy";

NSDate *someDate = [formatter dateFromString:@"12-22-2013"];
if (![appDelegate.database executeUpdate:@"INSERT INTO Observations (admin_id, teacher_id, observation_type, isvalid, date) VALUES (?, ?, ?, ?, ?)", @(appDelegate.admin_id), @(appDelegate.teacher_id), @(appDelegate.observationType), @"yes", someDate])
    NSLog(@"insert error: %@", [appDelegate.database lastErrorMessage]);

Or, if I wanted to select the dates between these two dates:

NSDate *startDate = [formatter dateFromString:@"12-20-2013"];
NSDate *endDate   = [formatter dateFromString:@"12-23-2013"];

NSString *query = @"create temp table search2 as select  Observationsid, date from Observations where admin_id=? AND teacher_id=? AND observation_type=? AND isvalid='yes' AND date BETWEEN ? AND ?";
if (![appDelegate.database executeUpdate:query, @(appDelegate.admin_id), @(appDelegate.teacher_id), @(appDelegate.observationType), startDate, endDate])
    NSLog(@"create error: %@", [appDelegate.database lastErrorMessage]);

query = @"SELECT * FROM search2";
FMResultSet *results = [appDelegate.database executeQuery:query];
if (!results)
    NSLog(@"select error: %@", [appDelegate.database lastErrorMessage]);
while ([results next])
    NSLog(@"%d %@", [results intForColumnIndex:0], [results dateForColumnIndex:1]);

If you want to avoid this NSDate logic, you could alternatively consciously store dates in a text format in YYYY-MM-DD format. That works, too. Again, see that Date and Time Functions page for a list of valid text formats for dates.