python Alchemy filter中datetime类型变量比较

python Alchemy filter中datetime类型变量比较是直接使用>、<或者>=或者<=来比较。

 python Alchemy filter中datetime类型变量比较，不能将datetime变为str再比较，否则条件无效

我的代码中，误以为要将datetime转化成str类型来比较，导致相关filter不起效果。代码如下：

id为46的update时间是 2024-01-02

    print("11111111111111111111111111111")
    query1=StuTest.query.filter(StuTest.id==46).filter(StuTest.update>'2023')
    print("query1:",query1)
    data1=query1.first()
    print(data1.update)
    print("2222222222222222222222222222")
    stu2 = StuTest.query.filter(StuTest.id==46).filter(str(StuTest.update) > '2026')
    print("query1:",stu2)
    data2=stu2.first()
    print(str(data2.update))

以上代码运行结果：

11111111111111111111111111111
query1: SELECT stu_test.id AS stu_test_id, stu_test.stu_name AS stu_test_stu_name, stu_test.stu_age AS stu_test_stu_age, stu_test.stu_class AS stu_test_stu_class, stu_test.`update` AS stu_test_update 
FROM stu_test 
WHERE stu_test.id = %(id_1)s AND stu_test.`update` > %(update_1)s
结果1： 2024-01-02 14:29:33
2222222222222222222222222222
query1: SELECT stu_test.id AS stu_test_id, stu_test.stu_name AS stu_test_stu_name, stu_test.stu_age AS stu_test_stu_age, stu_test.stu_class AS stu_test_stu_class, stu_test.`update` AS stu_test_update 
FROM stu_test 
WHERE stu_test.id = %(id_1)s
结果2： 2024-01-02 14:29:33

可以看到：加了str类型转换后的datetime条件过滤在sql语句中是无效条件。