Question

我是数据库新手，正在尝试使用SQLite最新版本3.25.2

我用文件信息建立了一个简单的数据库，将日期存储为ISO STRING（文本）。所有项目的查询显示：

sqlite3_exec(db, "SELECT * FROM dir", callback, 0, 0);

导致（通过回调输出）

system.NAME = New File.txt
modified = '2018-11-03 11:35:42'
system.NAME = ReadMe.txt
modified = '2018-11-01 10:43:21'
...

但是当我尝试查询一个特定的日期（比所述日期更新的文件）时，查询结果为空！？

sqlite3_exec(db, "SELECT * FROM dir WHERE modified > '2018-11-02 00:00:00'", callback, 0, 0);

从上面的数据库文件中可以看到，至少一个（New file.txt）应该与查询匹配。我还尝试过将日期存储为整数和实数，没有任何运气

这一定是愚蠢的，但我看不到它：（

Answer 1

使用：-

rc = sqlite3_exec(db,"CREATE TABLE IF NOT EXISTS dir (system_name TEXT, modified TEXT);",callback,0,&zErrMsg);
sqlite3_free(zErrMsg);
rc = sqlite3_exec(db,"INSERT INTO dir VALUES('New File.txt','2018-11-03 11:35:42'),('Readme.txt','2018-11-01 10:43:21');",callback,0,&zErrMsg);
sqlite3_free(zErrMsg);
rc = sqlite3_exec(db,"SELECT * FROM dir;",callback,0,&zErrMsg);
sqlite3_free(zErrMsg);
rc = sqlite3_exec(db,"SELECT * FROM dir WHERE modified > '2018-11-02 00:00:00';",callback,0,&zErrMsg);
sqlite3_free(zErrMsg);

结果：-

system_name = New File.txt
modified = 2018-11-03 11:35:42

system_name = Readme.txt
modified = 2018-11-01 10:43:21

system_name = New File.txt
modified = 2018-11-03 11:35:42

但是考虑到您的输出在输出中的日期周围有单引号，则：-

rc = sqlite3_exec(db,"CREATE TABLE IF NOT EXISTS dir (system_name TEXT, modified TEXT);",callback,0,&zErrMsg);
sqlite3_free(zErrMsg);
rc = sqlite3_exec(db,"DELETE FROM dir;",callback,0,&zErrMsg);
sqlite3_free(zErrMsg);
rc = sqlite3_exec(db,"INSERT INTO dir VALUES('New File.txt','''2018-11-03 11:35:42'''),('Readme.txt','''2018-11-01 10:43:21''');",callback,0,&zErrMsg);
sqlite3_free(zErrMsg); //<<<<<<<<<< ADDED single quotes
rc = sqlite3_exec(db,"SELECT * FROM dir;",callback,0,&zErrMsg);
sqlite3_free(zErrMsg);
rc = sqlite3_exec(db,"SELECT * FROM dir WHERE modified > '2018-11-02 00:00:00';",callback,0,&zErrMsg);
sqlite3_free(zErrMsg);

产生您的结果。基本上是因为将单引号作为值的一部分存储（至少在显示的uotput中如此显示）被考虑在内。

因此，解决该查询的方法是使用：-

sqlite3_exec(db,"SELECT * FROM dir WHERE modified > '''2018-11-02 00:00:00''';",callback,0,0);

但是，最好不要将值用单引号引起来。

查询SQLite数据库的日期

1 个答案: