Using the IOS SQLite database

Last Update:2015-12-22 Source: Internet

Author: User

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About SQLite is a lightweight, cross-platform, open-source database Engine. He has a great advantage in reading and writing efficiency, ease of operation and memory consumption, so it is very popular with mobile Developers. of course, SQLite also because it strives to be simple and efficient, but also restricts its processing of concurrent, massive Data. This blog is mainly about the use of SQLite and open Source Library Fmdb in iOS Development.Demo Address TP <ul> <ul> <li>Introduction to commonly used methods</li> </ul> </ul> <ol> <ol> <li>First Open the database</li> </ol> </ol><pre><pre>int result = Sqlite3_open_v2 (filename.utf8string, &db, sqlite_ioerr_read| sqlite_ioerr_write| sqlite_open_create, NULL); if (result = = sqlite_ok) { NSLog (@ "open True"); }</pre></pre>2. Create a table<pre><pre>// Create a table Const Char " CREATE TABLE IF not EXISTS t_demo (id integer PRIMARY KEY autoincrement,name text not null,age integer not NULL); " ; char *errmsg = NULL; = sqlite3_exec (db, sqlcreate, null, null, &errmsg); if (result = = sqlite_ok) { NSLog (@ "create True"); }</pre></pre>3. Execute SQL statements<pre>//Execute SQL statement//1. InsertNSString *sqlinsert = [nsstring stringwithformat:@"INSERT into T_demo (name,age) VALUES ('%@ ', '%d ');",@" one", +]; Sqlite3_exec (db, sqlinsert.utf8string, null, null,&errmsg); Sqlite3_exec (db, sqlinsert.utf8string, null, null,&errmsg); Sqlite3_exec (db, sqlinsert.utf8string, null, null,&errmsg); if(errmsg) {NSLog (@"Insert False"); } //2. EnquiryNSString *sqlquery = [nsstring stringwithformat:@"SELECT id,name,age from t_demo;"]; Sqlite3_stmt*STMT =NULL; //prepare to execute statement if(SQLITE3_PREPARE_V2 (db, sqlquery.utf8string,-1, &stmt, NULL) = =Sqlite_ok) { //Step into the execution of while(sqlite3_step (stmt) = =Sqlite_row) { intID = Sqlite3_column_int (stmt,0); ConstUnsignedChar*name = Sqlite3_column_text (stmt,1); intAge = Sqlite3_column_int (stmt,2); NSLog (@"%d***%s******%d", id,name,age); } } //ReleaseSqlite3_free (stmt);</pre> <ul> <ul> <li>Introduction to commonly used methods</li> </ul> </ul> <ol> <ol> <li>Open Database</li> </ol> </ol><pre>Sqlite3_open_v2 (Const Char*filename,/*Database name*/Sqlite3**ppdb,/*DB Instance*/ intFlags/*Flags*/ Const Char*zvfs/*Name of the VFS module to use*/ );</pre>2. Execute SQL statements<pre>sqlite3_exec (sqlite3*,/*DB Instance*/ Const Char*sql,/*SQL statements*/ int(*callback) (void*,int,Char**,Char**),/*Callback function*/ void*,/*1st argument to callback*/ Char**errmsg/*Error msg Written here*/ );</pre>3. Check SQL statement syntax<pre>SQLITE3_PREPARE_V2 (sqlite3*db,/*DB Instance*/ Const Char*zsql,/*SQL statements*/ intnbyte,/*Maximum length of zsql in Bytes.*/sqlite3_stmt**ppstmt,/*out:statement Handle*/ Const Char**pztail/*Out:pointer to unused portion of Zsql*/ );</pre>4. Query a row of data, if the query to a row of data, will return Sqlite_row<pre><pre> Sqlite3_step (sqlite3_stmt*);</pre></pre>5. Using stmt to get the value of a column<pre>DoubleSqlite3_column_double (sqlite3_stmt*,inticol);//floating point DataintSqlite3_column_int (sqlite3_stmt*,inticol);//Integral type DataSqlite3_int64 Sqlite3_column_int64 (sqlite3_stmt*,inticol);//Long-integer DataConst void*sqlite3_column_blob (sqlite3_stmt*,inticol);//binary Text DataConstUnsignedChar*sqlite3_column_text (sqlite3_stmt*,inticol);//String Data</pre>FMDB is a package for Sqlite. Source Address https://github.com/ccgus/fmdb, operation is the OC method, which is not familiar with or do not want to operate the C language method of the students is a relief.First import the SQLite system library, introduce the header file #import "FMDB.h"<pre>NSString *docdic =[nssearchpathfordirectoriesindomains (nsdocumentdirectory, nsuserdomainmask, YES) lastobject]; NSString*filename = [docdic stringbyappendingpathcomponent:@"fmdb.db"]; //Create database with empty path, CREATE database in memoryFmdb =[fmdatabase databasewithpath:filename]; [fmdb open]; //Execute SQL statements, add, delete, change are executeupdate methodsNSString *sqlcreate =@"CREATE TABLE IF not EXISTS t_demo (id integer PRIMARY KEY autoincrement,name text not null,age integer not NULL); "; BOOL Res=[fmdb executeupdate:sqlcreate]; NSString*sqlinsert = [nsstring stringwithformat:@"INSERT into T_demo (name,age) VALUES ('%@ ', '%d ');",@" one", +]; Res=[fmdb executeupdate:sqlinsert]; if(!res) {NSLog (@"error when creating DB table"); } Else{NSLog (@"success to creating DB table"); } //Execute QueryNSString *sqlquery = [nsstring stringwithformat:@"SELECT id,name,age from t_demo;"]; Fmresultset* rs =[fmdb executequery:sqlquery]; while([rs next]) {intId = [rs intforcolumn:@"ID"]; NSString* Name = [rs stringforcolumn:@"name"]; NSString* age = [rs Stringforcolumn:@" age"]; NSLog (@"ID =%d, name =%@, age =%@", Id, name, age); }</pre>Using the IOS SQLite database

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