SQLite 常用SQL语句

1.可视化软件中

//创建表 create table （表名，字段名，字段类型）（integer：有符号整型，text：文本类型，real：浮点型）

//primary key ：主键（唯一+自增）

//create tableif not exists需要添加后面的 （如果表不存在，就创建；否则不创建）

//create table people (id integer, name text, age integer, class text);

create table if not exists people (id integer primary key, name text, age integer, class text);

// where 选择条件; and 与； or 或；

//增：insert into

insert into people (id,name,age,class) values (1,'Jonny',20,'class1512');

insert into people (id,name,age,class) values (2,'Maggie',19,'class1501');

insert into people (id,name,age,class) values (3,'Bob',21,'class1511');
//改：update ... set

update people set class='class1510' where name='Jonny';
//查：select from

select * from people;

select name from people;

select * from people where age>19 and age<22;
//删： delete from

delete from people where name='Maggie';

2.代码中

//用于创建连接

sqlite3_open(<#const char *filename#>, <#sqlite3 **ppDb#>);

//用于创建sql文件、增、删、改

sqlite3_exec(<#sqlite3 *#>, <#const char *sql#>, <#int (*callback)(void *, int, char **, char **)#>, <#void *#>, <#char **errmsg#>);

//用于查询

sqlite3_prepare_v2(<#sqlite3 *db#>, <#const char *zSql#>, <#int nByte#>, <#sqlite3_stmt **ppStmt#>, <#const char **pzTail#>);

- (void)createDBAndDataOperation {

    //1.创建数据库文件(保存在Document路径下)

    NSString *documentPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask,YES)firstObject];

    NSString *databasePath = [documentPathstringByAppendingPathComponent:@"text.db"];

    /**

     *  如果不存在test.db ,创建并打开；否则打开

     * 参数1：数据库文件所在的路径

     * 参数2：指向已经创建并打开的数据库对象(打开连接)

     */

    sqlite3 *db =NULL;

    int ret =sqlite3_open([databasePathcStringUsingEncoding:NSUTF8StringEncoding],
&db);

    //ret != 0

    if (ret !=SQLITE_OK) {

        NSLog(@"创建数据库文件失败：%s",sqlite3_errmsg(db));

    }

    //2.创建表(主键primary
key:唯一+自增)

    constchar *createTable ="create table
if not exists people (id integer primary key,name text,age integer,height real)";

    char *errmsg =NULL;

    ret = sqlite3_exec(db, createTable,NULL,NULL,
&errmsg);

    if (ret !=SQLITE_OK) {

        NSLog(@"创建表失败:%s",errmsg);

    }

   //增、删、改、查

   //id是主键，自增不需要给值

    //增（代码每执行一次都会添加一条相同的记录，id自增）

    constchar *insertRecord ="insert into
people (name,age,height) values ('Jonny',19,1.85)";

    ret = sqlite3_exec(db, insertRecord,NULL,NULL,
&errmsg);

    if (ret !=SQLITE_OK) {

        NSLog(@"插入数据失败:%s",errmsg);

    }

    //改

    constchar *updateRecord ="update people
set height= 1.70 where id=1";

    ret = sqlite3_exec(db, updateRecord,NULL,NULL,
&errmsg);

    if (ret !=SQLITE_OK) {

        NSLog(@"修改数据失败:%s",errmsg);

    }

    //删

    constchar *deleteRecord ="delete from
people where height=1.85";

    ret = sqlite3_exec(db, deleteRecord,NULL,NULL,
&errmsg);

    if (ret !=SQLITE_OK) {

        NSLog(@"删除数据失败:%s",errmsg);

    }

    //查

    constchar *selectRecord ="select * from people";

    sqlite3_stmt *stmt;

    //第3个参数：
-1 从头执行到尾

    ret = sqlite3_prepare_v2(db, selectRecord, -1, &stmt,NULL);

    if (ret ==SQLITE_OK) {

        //查询成功

        //循环取出相应的值

        while (sqlite3_step(stmt) ==SQLITE_ROW)
{

            //第2个参数：所要查询的参数的下标

            constunsignedchar *name =sqlite3_column_text(stmt,
1);

            constint age =sqlite3_column_int(stmt,
2);

            constdouble height =sqlite3_column_double(stmt,
3);

            NSLog(@"name:%s,age:%d,height:%.2f",name,age,height);

        }

    }

   //收尾工作：释放stmt内存、断开数据库的连接

    sqlite3_finalize(stmt);

    sqlite3_close(db);    

}

3.使用第三方(FMDB)

- (void)createDataBaseAndDataOperation {

    //1.创建数据库

    NSString *documentPath = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
NSUserDomainMask,
YES) firstObject];

    NSString *dbFilePath = [documentPath
stringByAppendingPathComponent:@"fmdb.db"];

   
//仅仅创建数据库文件，并没有打开

    FMDatabase *database = [FMDatabase
databaseWithPath:dbFilePath];

    //2.创建表

    if ([database
open]) {

        BOOL isSucess = [database
executeUpdate:@"create table if not exists people (id integer primary key, name text, height real)"];

        if (!isSucess) {

            NSLog(@"创建表失败:%@",database.lastError);

        }

    }

    //open，close
可以只写一次，在database开头与末尾执行，此处模拟单个方法（创建，增、删、改、查）

    [database close];

    //3.插入数据

    if ([database
open]) {

        BOOL isSucess = [database
executeUpdate:@"insert into people (name,height) values ('Bob',1.85)"];

        if (!isSucess) {

            NSLog(@"插入数据失败:%@",database.lastError);

        }

    }

    [database close];

    //4.查询数据

    if ([database
open]) {

        FMResultSet *resultSet = [database
executeQuery:@"select * from people"];

        while ([resultSet
next]) {

           
//从记录中获取每个字段（根据不同的字段类型选取不同的方法）

            //根据字段名查询

            NSString *nameStr = [resultSet
stringForColumn:@"name"];

            //根据下标查询

            //[resultSet stringForColumnIndex:1]

            double height = [resultSet
doubleForColumn:@"height"];

            NSLog(@"name:%@,height:%.2f",nameStr,height);

        }

    }

    [database close];