数据库语句记录

    NSString*queryString = [NSString stringWithFormat:@"SELECT count(*) allCount FROM UserInfoTable  WHERE forMyId = %@ AND nickname like '不%%'",[WHL_SelfInfoModel sharedInstance].user_uid];
    [[self sharedInstance].userBaseQueue inTransaction:^(FMDatabase* db, BOOL* rollback) {
        FMResultSet *s = [db executeQuery:queryString];
        while ([s next]) {
            int allCount = [s intForColumn:@"allCount"];
            int totalCount = [s intForColumnIndex:0];
        }
    }];NSString*queryString = [NSString stringWithFormat:@"SELECT count(*) allCount FROM UserInfoTable  WHERE forMyId = %@ AND nickname like '不%%'",[WHL_SelfInfoModel sharedInstance].user_uid];
    [[self sharedInstance].userBaseQueue inTransaction:^(FMDatabase* db, BOOL* rollback) {
        FMResultSet *s = [db executeQuery:queryString];
        while ([s next]) {
            int allCount = [s intForColumn:@"allCount"];
            int totalCount = [s intForColumnIndex:0];
        }
    }];

allCount = totalCount = 2

    NSString*queryString = [NSString stringWithFormat:@"SELECT * FROM UserInfoTable,GroupListTable WHERE UserInfoTable.forMyId = GroupListTable.forMyId"];

UserInfoTable 表有20个字段,GroupListTable 有21个字段,查询出来是41个

创建多列索引

CREATE TABLE if not exists GroupListTable g_id text not null,forMyId integer not null,CONSTRAINT uc_g_id UNIQUE (g_id,forMyId)

autoincrement 不建议使用
CONSTRAINT用意解析
SQLite INSERT OR REPLACE使用

FMDBDatabaseQueue 的内部实现逻辑

- (void)inDatabase:(__attribute__((noescape)) void (^)(FMDatabase *db))block {
#ifndef NDEBUG
    /* Get the currently executing queue (which should probably be nil, but in theory could be another DB queue
     * and then check it against self to make sure we're not about to deadlock. */
    FMDatabaseQueue *currentSyncQueue = (__bridge id)dispatch_get_specific(kDispatchQueueSpecificKey);
    assert(currentSyncQueue != self && "inDatabase: was called reentrantly on the same queue, which would lead to a deadlock");
#endif
    
    FMDBRetain(self);
    
    dispatch_sync(_queue, ^() {
        
        FMDatabase *db = [self database];
        
        block(db);
        
        if ([db hasOpenResultSets]) {
            NSLog(@"Warning: there is at least one open result set around after performing [FMDatabaseQueue inDatabase:]");
            
#if defined(DEBUG) && DEBUG
            NSSet *openSetCopy = FMDBReturnAutoreleased([[db valueForKey:@"_openResultSets"] copy]);
            for (NSValue *rsInWrappedInATastyValueMeal in openSetCopy) {
                FMResultSet *rs = (FMResultSet *)[rsInWrappedInATastyValueMeal pointerValue];
                NSLog(@"query: '%@'", [rs query]);
            }
#endif
        }
    });
    
    FMDBRelease(self);
}

可以看出来其内部维护了一个串行队列,在当前线程同步执行此任务.如次以来不建议在主线程执行update、insert 等耗时量较大的任务。