Common SQL usage in Fmdb

Everyone in the work, the most commonly used is to increase, delete, check, change ...

The corresponding statement in SQL is: INSERT DELETE SELECT UPDATE

First, you can visualize the management database using a tool called "SQLite database Browser".

Then add the database file to the resource directory, and then install the database using the following code, which is copied to the doc directory:

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2. Install File to Doc dir
4. -(BOOL) Installfileofname: (NSString *) FileName {
8. NSString *pathfordoc = nil;
10. NSString *pathforres = nil;
14. Pathfordoc = [Nshomedirectory () stringbyappendingformat:@"/documents/%@", FileName];
18. //nslog (@ "%@", Pathfordoc);
22. if ([[Nsfilemanager defaultmanager] fileexistsatpath:pathfordoc] = = YES) {
24. return NO;
26. }Else {
30. Pathforres = [[NSBundle mainbundle] pathforresource:filename oftype:[filename pathextension]];
34. NSData *filedata = [NSData datawithcontentsoffile:pathforres];
36. [[Nsfilemanager Defaultmanager] Createfileatpath:pathfordoc contents:filedata Attributes:nil];
40. return YES;
42. }
44. }

The above method, you can call directly, pass a database file name, then it will copy it to the doc directory.

Here are some Fmdb operations to install and open the database:

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2. if ([Self installfileofname:@"test_db"] = = YES) {
4. NSLog (@"Install database success.");
6. }Else {
8. NSLog (@"install database fail.");
10. }
14. NSString *dbpath = [Nshomedirectory () stringbyappendingformat:@"/documents/%@", @"test_db"];
18. //nslog (@ "Database path:%@", DbPath);
22. Fmdatabase *FM = [Fmdatabase Databasewithpath:dbpath];
26. if ([fm open] = = YES) {
28. NSLog (@"Open database success.");
30. }Else {
32. NSLog (@"Open database fail.");
34. return;
36. }

Next, we can start testing the various SQL statements:

Insert a record into the database:

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1. BOOL operaresult = [fm executeupdate:@"INSERT into Test_tab (name,age,mail) VALUES (?,?,?)" @"good" @"4" @  "[email protected]"];

To modify a record in a database:

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1. BOOL operaresult = [FM executeupdate:@] UPDATE test_tab SET name=?  Where name=? ", @" 123 ", @" good "];

To delete a record from the database:

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1. BOOL operaresult = [fm executeupdate:@"DELETE from Test_tab WHERE name=?", @"Jiajia"];

Get records from the database and sort in descending order:

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1. Fmresultset *s = [fm executequery:@"SELECT * from Test_tab ORDER by age DESC"];

Common SQL usage in Fmdb