sql语句拼接

1.拼接字段

#pragma mark - 拼接sql语句
-(NSString *)sql_keys:(NSArray *)attributes{
    if (attributes.count <= 0) {
        return nil;
    }
    
    NSMutableString *keys = [NSMutableString string];
    int sum = 0;
    [keys appendString:@"("];
    for (NSString *key in attributes) {
        sum += 1;
        if (sum < attributes.count) {
            [keys appendFormat:@"%@,",key];
        }else{
            [keys appendFormat:@"%@",key];
        }
    }
    [keys appendString:@")"];
    return keys;
}

2.拼接占位符

-(NSString *)sql_values:(NSArray *)attributes{
    
    if (attributes.count <= 0) {
        return nil;
    }
    
    NSMutableString *values = [NSMutableString string];
    [values appendString:@"("];
    for (int i = 0; i < attributes.count; i++) {
        if (i < attributes.count-1) {
            [values appendFormat:@"?,"];
        }else{
            [values appendFormat:@"?"];
        }
    }
    [values appendString:@")"];
    return values;
}

3.拼接sql

-(NSString *)sqls:(NSArray *)attributes{
    
    if (attributes.count <= 0) {
        return nil;
    }
    
    NSMutableString *sql = [NSMutableString string];
    NSString *keys   = [self sql_keys:attributes];
    NSString *values = [self sql_values:attributes];

    [sql appendString:keys];
    [sql appendString:@" values "];
    [sql appendString:values];

    NSLog(@"sql ============== %@",sql);
    return sql;
}

4.全语句拼接

-(NSString *)insertTable:(NSString *)tableName attributes:(NSArray *)attributes{
    
    NSString *message = [NSString stringWithFormat:@"%@ %@ 表名不能为空",NSStringFromClass([self class]),NSStringFromSelector(_cmd)];
    NSAssert(tableName, message);
    
    if (!tableName || tableName.length <= 0) {
        return nil;
    }
    
    if (!attributes || attributes.count <= 0) {
        return nil;
    }
   
    NSString *sql = [NSString stringWithFormat:@"INSERT OR REPLACE INTO %@ %@",tableName,[self sqls:attributes]];
    return sql;
}

5.来吧展示

    
NSArray *attributes = @[@"uid",@"age",@"name",@"avatar",@"gender"];
NSString *sql = [self insertTable:tb_base_users attributes:attributes];

sql  ===== INSERT OR REPLACE INTO  (uid, age, name, avatar,gender) values (?,?,?,?,?)