为什么我的查询在SQLITE中返回错误的数据集？

Question

我有一个名为'Date'的列，这些日期格式为m / d / yyyy，当我查询“从table_nm选择日期'2015年1月20日'和'2015年1月9日之间的日期'时我得到错误的结果。

"1/2/2015"
"1/5/2015"
"1/6/2015"
"1/7/2015"
"1/8/2015"
"1/9/2015"
"1/20/2015"
"1/21/2015"
"1/22/2015"
"1/23/2015"
"1/26/2015"
"1/27/2015"
"1/28/2015"
"1/29/2015"
"1/30/2015"

Answer 1

您的问题是日期不是SQLite接受的格式。

有效格式可在SQL As Understood By SQLite - Date And Time Functions - Time Strings

找到

您的日期使用的格式特别笨拙，因为月份和日期可以是1或2个字符。最可能合适的格式是YYYY-MM-DD，例如： 2015年1月30日

您可以使用以下内容作为解决方案的基础： -

SELECT  *,
    CASE 
        WHEN CAST(month AS INTEGER) < 10 AND CAST(dayinmonth AS INTEGER) < 10 THEN year||'-0'||month||'-0'||dayinmonth
        WHEN CAST(month AS INTEGER) < 10 AND CAST(dayinmonth AS INTEGER) >= 10 THEN year||'-0'||month||'-'||dayinmonth
        WHEN CAST(month AS INTEGER) >= 10 AND CAST(dayinmonth AS INTEGER) < 10 THEN year||'-'||month||'-0'||dayinmonth
        WHEN CAST(month AS INTEGER) >= 10 AND CAST(dayinmonth AS INTEGER) >= 10 THEN year||'-'||month||'-'||dayinmonth
    END AS newdate
FROM (
    SELECT 
        *,
        substr(date,length(date)-3) AS year, 
        substr(date,1,instr(date,'/')-1) AS month,
        substr(
            substr(date, instr(date,'/')+1),
            1,
            instr(substr(date, instr(date,'/')+1),'/') -1
            )
            AS dayinmonth
    FROM mytable002 
) 
WHERE newdate BETWEEN '2015-01-02' AND '2015-01-09'

测试结果： -

mytable002用于测试的表格如下： -

• 实际上有更多行
添加了
• date2和date3，以帮助演示其他列的包含。

结果输出为： -

注释

• mytable002必须相应更改。
• 结果数据包括其他列（原始带下划线的蓝色新列突出显示）
  • 使用* *所有原始列将在结果数据中可用

额外评论： -

  

谢谢，我已经使用python将这些数据导入sqlite，   转换每一行并不容易。

以上可能是非常简单转换的基础。您可以添加一列，然后根据上述内容将重新格式化的日期存储到该列中。

e.g。 ： -

ALTER TABLE mytable002 ADD COLUMN newcolumn TEXT;
WITH updatedata (newdate,olddate) AS (
    SELECT 
        CASE 
            WHEN CAST(month AS INTEGER) < 10 AND CAST(dayinmonth AS INTEGER) < 10 THEN year||'-0'||month||'-0'||dayinmonth
            WHEN CAST(month AS INTEGER) < 10 AND CAST(dayinmonth AS INTEGER) >= 10 THEN year||'-0'||month||'-'||dayinmonth
            WHEN CAST(month AS INTEGER) >= 10 AND CAST(dayinmonth AS INTEGER) < 10 THEN year||'-'||month||'-0'||dayinmonth
            WHEN CAST(month AS INTEGER) >= 10 AND CAST(dayinmonth AS INTEGER) >= 10 THEN year||'-'||month||'-'||dayinmonth
        END AS newdate,
        date AS olddate
    FROM (
        SELECT 
            *,
            substr(date,length(date)-3) AS year, 
            substr(date,1,instr(date,'/')-1) AS month,
            substr(
                substr(date, instr(date,'/')+1),
                1,
                instr(substr(date, instr(date,'/')+1),'/') -1
                )
                AS dayinmonth
        FROM mytable002 
        ) 
    )
UPDATE mytable002 
SET newcolumn = (
    SELECT newdate
    FROM updatedata
    WHERE mytable002.date = olddate
    )
;