Oracle（SQL 语句）- 将 CASE 与 WHERE CLAUSE 结合使用答案

【问题标题】：Oracle (SQL Statements) - Using CASE with WHERE CLAUSEOracle（SQL 语句）- 将 CASE 与 WHERE CLAUSE 结合使用
【发布时间】：2020-04-07 14:35:45
【问题描述】：

尊敬的专家，我准备了一个 SQL 报告，以使用 CASE 显示带有 Format_Check 验证的数据。我在下面提供了示例、问题和期望：

表结构：enter image description here

SQL 语句：

SELECT 

ID,PRODUCT,COMMENTS

CASE WHEN SUBSTR(COMMENTS,1,35)=REGEXP_SUBSTR (COMMENTS,'(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\s)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\s)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\s)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)',1,1)
AND
LENGTH(TRIM(REGEXP_SUBSTR (COMMENTS, '(\S*)(\s)', 1, 2)))=8 
AND
REGEXP_LIKE(TRIM(REGEXP_SUBSTR (COMMENTS, '(\S*)(\s)', 1, 1)),'(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)')
THEN 'Correct Format'
ELSE 'Incorrect_Format'
END AS Format_Check

FROM TEST_TABLE

SQL 输出： enter image description here

SQL 输出说明：

检查 COMMENTS 列是否为 35 个字符长，还检查格式数字和空格。 SUBSTR(COMMENTS,1,35)=REGEXP_SUBSTR (评论,'(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\s)(\d)(\d)(\ d)(\d)(\d)(\d)(\d)(\d)(\s)(\d)(\d)(\d)(\d)(\d)(\d) (\d)(\d)(\s)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)',1,1)

检查第一个空格后的 cmets 是否为 8 个字符长 LENGTH(TRIM(REGEXP_SUBSTR (COMMENTS, '(\S*)(\s)', 1, 2)))=8

检查前 8 个字符是数字/数字。 REGEXP_LIKE(TRIM(REGEXP_SUBSTR (COMMENTS, '(\S*)(\s)', 1, 1)),'(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)')

预期：

我只需要在执行 SQL 时显示“格式不正确”的 cmets，我不希望看到“正确格式”的 cmets。但是，我需要您就这种情况是否与 WHERE 子句一起使用以仅显示不正确的格式 COMMENTS 提出建议。我参考了以前与 WHERE 和 CASE 相关的查询，但是我无法弄清楚如何在 WHERE 子句中传递我的案例。感谢您的帮助。

【问题讨论】：

标签： sql oracle case where-clause

【解决方案1】：

如果你想显示不正确的格式列，你可以用另一个包装你的查询：

SELECT id, product, comment, format_check
  FROM (
        SELECT id, product, comment, CASE WHEN .... END AS format_check
          FROM test_table
       )
 WHERE format_check = 'Incorrect_Format';

顺便说一句，如果您使用 SQL 而不是图像显示表和数据，您的问题会更容易回答，例如：

CREATE TABLE test_table (id NUMBER, product VARCHAR2(10), comments VARCHAR2(50));
INSERT INTO  test_table VALUES (1,'Laptop', '00000001 01012020 02022020 03032020');
INSERT INTO  test_table VALUES (1,'PC',     '   00000001 01012020 02022020 0034');

此外，我相信正则表达式可以简化。如果您有兴趣，请提供更多详细信息...

【讨论】：

【解决方案2】：

如果您根本不希望在结果中看到正确的格式，那么您可以省略select 子句中的格式计算。而是在Where 子句中使用它，如下所示：

SELECT ID,
       PRODUCT,
       COMMENTS,
      'Incorrect_Format' AS format_check
  FROM TEST_TABLE
 WHERE CASE WHEN SUBSTR(COMMENTS,1,35)=REGEXP_SUBSTR (COMMENTS,'(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\s)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\s)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\s)(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)',1,1)
AND
LENGTH(TRIM(REGEXP_SUBSTR (COMMENTS, '(\S*)(\s)', 1, 2)))=8 
AND
REGEXP_LIKE(TRIM(REGEXP_SUBSTR (COMMENTS, '(\S*)(\s)', 1, 1)),'(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)')
THEN 'Correct Format'
ELSE 'Incorrect_Format'
END AS = 'Incorrect_Format'

【讨论】：