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

Question

Dear Experts, I preparing an SQL report to display the data with Format_Check validations using CASE. I have provided the example,issues and expectation below:

Table Structure: enter image description here

SQL Statement:

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 Output: enter image description here

SQL Output Explanation:

1. Checks whether COMMENTS column is 35 Character long, also checks the format numbers and spaces. 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)

2. Checks whether the comments after first space is 8 characters long LENGTH(TRIM(REGEXP_SUBSTR (COMMENTS, '(\S*)(\s)', 1, 2)))=8

3. Checks the first 8 characters is digit/number. REGEXP_LIKE(TRIM(REGEXP_SUBSTR (COMMENTS, '(\S*)(\s)', 1, 1)),'(\d)(\d)(\d)(\d)(\d)(\d)(\d)(\d)')

Expectation:

I need only the 'Incorrect Format' comments to be displayed when the SQL is executed, I don't wish to see the 'Correct Format' comments. However I need your advise on whether this case be used with WHERE clause to display only incorrect format COMMENTS alone. I referred previous queries related to WHERE and CASE, however I can't figure out on how pass my case in WHERE clause. Thanks for your help.

Answer 1

If you want to display the incorrect format columns, you can wrap your query with another one:

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';

BTW, your question is easier to answer if you show your table and data with SQL instead of an image, for instance like:

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');

Furthermore, I believe the regular expression can be simplified. Please provide a bit more detail if you're interested...

Answer 2

If you do not wish to see the correct format in the result at all then you can omit the calculation of the format in select clause. Rather use it in Where clause as follows:

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'