iOS Learning notes-the app for SQLite

1 //2 //HMVIEWCONTROLLER.M3 //Application of 02-sqlite4 //5 //Created by Apple on 14-7-24.6 //Copyright (c) 2014 Heima. All rights reserved.7 //8 9 #import "HMViewController.h"Ten #import<sqlite3.h> One  A @interfaceHmviewcontroller () --(ibaction) insert; --(ibaction) update; the-(ibaction) Delete; --(ibaction) Select; - //db is the symbol of the database, if you want to do crud, you have to operate DB this instance -@property (nonatomic, assign) Sqlite3 *db; + @end -  + @implementationHmviewcontroller A  at- (void) Viewdidload - { - [Super Viewdidload]; -      -     //get the path to the database file -NSString *doc =[Nssearchpathfordirectoriesindomains (NSDocumentDirectory, Nsuserdomainmask, YES) lastobject]; inNSString *filename = [Doc stringbyappendingpathcomponent:@"Students.sqlite"]; -     //Convert OC String to C language string to     Const Char*cfilename =filename. utf8string; +     //1. Open the database (if the database file does not exist, the Sqlite3_open function automatically creates the database file) -     intresult = Sqlite3_open (cFileName, &_db); the     if(Result = = SQLITE_OK) {//Open Success *NSLog (@"successfully opened database"); $         Panax Notoginseng         //2. Create a watch -         Const Char*sql ="CREATE TABLE IF not EXISTS t_student (ID integer PRIMARY KEY autoincrement, name text NOT NULL, age integer NOT NULL); "; the         Char*erromsg =NULL; +result = Sqlite3_exec (self.db, SQL, NULL, NULL, &erromsg); A         if(Result = =SQLITE_OK) { theNSLog (@"successful creation of a table"); +}Else { -             //printf ("Genesis failure--%s--%s-%d", Erromsg, __file__, __line__); $NSLog (@"Create a table failure--%s--%@-%d", erromsg, [NSString stringwithutf8string:__file__], __line__); $         } -}Else { -NSLog (@"failed to open database"); the     } - }Wuyi  the-(ibaction) Insert { -      for(inti =0; i< -; i++) { Wu         //1. Splicing SQL statements -NSString *name = [NSString stringWithFormat:@"jack-%d", Arc4random_uniform ( -)]; About         intAge = Arc4random_uniform ( -) + -; $NSString *sql = [NSString stringWithFormat:@"INSERT into T_student (name, age) VALUES ('%@ ',%d);", name, age]; -          -         //2. Execute SQL statements -         Char*erromsg =NULL; ASqlite3_exec (self.db, SQL. Utf8string, NULL, NULL, &erromsg); +         if(erromsg) { theNSLog (@"failed to insert data--%s", erromsg); -}Else { $NSLog (@"successfully inserting data"); the         } the     } the } the  --(ibaction) Update { in     //different than insert only SQL statement the } the  About-(ibaction) Delete { the     //different than insert only SQL statement the } the  +-(ibaction) Select { -     Const Char*sql ="SELECT ID, name, age from T_student WHERE age <=;"; the     //Preparation before queryingBayi     //-1 means the system automatically calculates the length of the SQL statement the     //sqlite3_stmt: Used to fetch data theSqlite3_stmt *stmt =NULL; -     if(SQLITE3_PREPARE_V2 (self.db, SQL,-1, &stmt, NULL) = = SQLITE_OK) {//no problem with SQL statements -NSLog (@"no problem with query statements"); the          the         //each time the Sqlite3_step function is adjusted, stmt points to the next record the          while(Sqlite3_step (stmt) = = Sqlite_row) {//Find a record the             //Remove Data -              the             //Remove the value of the No. 0 column field (the value of type int) the             intID = Sqlite3_column_int (stmt,0); the             94             //Remove the value of the 1th column field (the value of Tex type) the             ConstUnsignedChar*name = Sqlite3_column_text (stmt,1); the              the             //Remove the value of the 2nd column field (the value of type int)98             intAge = Sqlite3_column_int (stmt,2); About              -NSLog (@"%d%s%d", ID, name, age);101         }102}Else {103NSLog (@"problem with query statement");104     } the }106 @end