MySql 版本 8.0.17 平均 datediff

Question

In the table stored an a database MySql version 8.0.17 I have these four field set as datetime type

+---------------------+-----------+---------------------+------------+
| tdate               | tigx      | tclosed             | tcompleted |
+---------------------+-----------+---------------------+------------+

• the field tdate never null ;
• the field tigx it could be null ;
• the field tclosed it could be null ;
• the field tcompleted it could be null ;

Now I get the average datediff respecting this sequence

1. If tclosed IS NOT NULL AND tcompleted IS NOT NULL AND tigx IS NOT NULL the AVG is ROUND(AVG(DATEDIFF(tclosed, tdate)),1)
2. If tclosed IS NULL AND tcompleted IS NULL AND tigx IS NULL the AVG is ROUND(AVG(DATEDIFF(CURDATE(), tdate)),1)

But if at least one of the fields tigx or tclosed or tcompleted is null I have to take the first populated field from tigx or tclosed or tcompleted ... and using this first populated field for get the average datediff.

Here I am stuck... any suggestion?

My query below

SELECT
    tkt,
    tdate,
    tstate,
    tigx,
    tclosed,
    tcompleted,
CASE        
        WHEN ( tclosed IS NOT NULL AND tcompleted IS NOT NULL AND tigx IS NOT NULL ) THEN
        ROUND( AVG( DATEDIFF( tclosed, tdate )), 1 ) 
        WHEN ( tclosed IS NULL AND tcompleted IS NULL AND tigx IS NULL ) THEN
        ROUND( AVG( DATEDIFF( CURDATE(), tdate )), 1 ) 
    END AS `avg` 
FROM
    `tbl_c` 
WHERE
    NOT ( `tkt` LIKE '%I%' OR `tkt` LIKE '%L%' AND tstate IN ( 'Closed' ) AND tigx IS NULL AND tclosed IS NULL AND tcompleted IS NULL ) 
ORDER BY
    tdate DESC;

UPDATE 2

SELECT
    tkt,
    tdate,
    tstate,
    tigx,
    tclosed,
    tcompleted,
CASE        
        WHEN ( tclosed IS NOT NULL AND tcompleted IS NOT NULL AND tigx IS NOT NULL ) THEN
        ROUND( AVG( DATEDIFF( tclosed, tdate )), 1 ) 
        WHEN ( tclosed IS NULL AND tcompleted IS NULL AND tigx IS NULL ) THEN
        ROUND( AVG( DATEDIFF( CURDATE(), tdate )), 1 ) 

        WHEN COALESCE(tclosed,tcompleted,tigx) THEN 
        ROUND(AVG(DATEDIFF(?????, tdate)),1)

    END AS `avg` 
FROM
    `tbl_c` 
WHERE
    NOT ( `tkt` LIKE '%I%' OR `tkt` LIKE '%L%' AND tstate IN ( 'Closed' ) AND tigx IS NULL AND tclosed IS NULL AND tcompleted IS NULL ) 
ORDER BY
    tdate DESC;

UPDATE

SELECT
    tkt,
    tdate,
    tstate,
    tigx,
    tclosed,
    tcompleted,
CASE        
        WHEN ( tclosed IS NOT NULL AND tcompleted IS NOT NULL AND tigx IS NOT NULL ) THEN
        ROUND( AVG( DATEDIFF( tclosed, tdate )), 1 ) 
        WHEN ( tclosed IS NULL AND tcompleted IS NULL AND tigx IS NULL ) THEN
        ROUND( AVG( DATEDIFF( CURDATE(), tdate )), 1 ) 
        WHEN COALESCE ( tclosed ) THEN
        ROUND( AVG( DATEDIFF( tcompleted, tdate )), 1 ) 
        WHEN COALESCE ( tcompleted ) THEN
        ROUND( AVG( DATEDIFF( tigx, tdate )), 1 ) 
        WHEN COALESCE ( tigx ) THEN
        ROUND( AVG( DATEDIFF( tclosed, tdate )), 1 ) 
    END AS `avg` 
FROM
    `tbl_c` 
WHERE
    NOT ( `tkt` LIKE '%I%' OR `tkt` LIKE '%L%' AND tstate IN ( 'Closed' ) AND tigx IS NULL AND tclosed IS NULL AND tcompleted IS NULL ) 
ORDER BY
    tdate DESC;

Answer 1

You seem to be struggling with this, following is at least conceptually correct(not sure about the bracketing and outcome)

CASE        
        WHEN ( tclosed IS NOT NULL AND tcompleted IS NOT NULL AND tigx IS NOT NULL ) THEN
             ROUND( AVG( DATEDIFF( tclosed, tdate )), 1 ) 
        WHEN ( tclosed IS NULL AND tcompleted IS NULL AND tigx IS NULL ) THEN
            ROUND( AVG( DATEDIFF( CURDATE(), tdate )), 1 ) 
        else
            ROUND(AVG(DATEDIFF(COALESCE(tclosed,tcompleted,tigx), tdate)),1
END AS `avg` 

Answer 2

I have had a go at this one for you, but I have had to make 2 assumptions:

1. Dates have rising values across the columns: tdate <= tigx <= tclosed <= tcompleted
2. All date values are <= CURRENT_DATE

Given those assumptions are correct, you might like to have a look at this. My solution is for you to create a view to handle your date / null logic. I hope it helps:

    /*
Create some test data
need this number generator to create data rows
*/
CREATE OR REPLACE VIEW `number_generator_16` AS 
SELECT 0 AS `n` 
UNION ALL SELECT 1 AS `1` 
UNION ALL SELECT 2 AS `2` 
UNION ALL SELECT 3 AS `3` 
UNION ALL SELECT 4 AS `4` 
UNION ALL SELECT 5 AS `5` 
UNION ALL SELECT 6 AS `6` 
UNION ALL SELECT 7 AS `7` 
UNION ALL SELECT 8 AS `8` 
UNION ALL SELECT 9 AS `9` 
UNION ALL SELECT 10 AS `10` 
UNION ALL SELECT 11 AS `11` 
UNION ALL SELECT 12 AS `12` 
UNION ALL SELECT 13 AS `13` 
UNION ALL SELECT 14 AS `14` 
UNION ALL SELECT 15 AS `15`
;

/*Create a table to contain test data*/
DROP TABLE IF EXISTS `a_testdatestdate`;
CREATE TABLE `a_testdatestdate` (
  `n` INT(10) SIGNED NOT NULL,
  `tdate` DATE NOT NULL,
  `tigx` DATE DEFAULT NULL,
  `tclosed` DATE DEFAULT NULL,
  `tcompleted` DATE DEFAULT NULL
) ENGINE=INNODB DEFAULT CHARSET=utf8;

/*
(Truncate - if necessary) and repopulate
TRUNCATE TABLE `a_testdatestdate`;
 
This statement generates a series of 100 rows where 
there is always a value in tdate
the other 4 columns are populated with rising date values
Populated with data in columns 2/3/4/(2-3)/(2-4)/(3-4)/(2-3-4)
ASSUMPTIONS:
1) dates have rising values across the columns: tdate <= tigx <= tclosed <= tcompleted
2) all date values are <= CURRENT_DATE
*/
SET @STARTDATE = DATE_ADD(CURRENT_DATE, INTERVAL -200 DAY);

INSERT INTO `a_testdatestdate` (`n`, `tdate`, `tigx`, `tclosed`, `tcompleted`)
SELECT 
`n`.`n`,
DATE_FORMAT(DATE_ADD( @STARTDATE, INTERVAL `n`.`n` DAY),"%Y-%m-%d") AS `tDate`
,  CASE  
    WHEN n.n BETWEEN 10 AND 40 THEN  DATE_FORMAT(DATE_ADD( @STARTDATE, INTERVAL `n`.`n` + 1 DAY),"%Y-%m-%d")
    WHEN n.n BETWEEN 70 AND 80 THEN  DATE_FORMAT(DATE_ADD( @STARTDATE, INTERVAL `n`.`n` + 2 DAY),"%Y-%m-%d")
    ELSE NULL
   END
,  CASE  
    WHEN n.n BETWEEN 30 AND 50 THEN  DATE_FORMAT(DATE_ADD( @STARTDATE, INTERVAL `n`.`n` + 3 DAY),"%Y-%m-%d")
    WHEN n.n BETWEEN 90 AND 100 THEN  DATE_FORMAT(DATE_ADD( @STARTDATE, INTERVAL `n`.`n` + 4 DAY),"%Y-%m-%d")
    ELSE NULL
   END
,  CASE  
    WHEN n.n BETWEEN 35 AND 60 THEN  DATE_FORMAT(DATE_ADD( CURRENT_DATE, INTERVAL `n`.`n` + 6 DAY),"%Y-%m-%d")
    WHEN n.n BETWEEN 70 AND 80 THEN  DATE_FORMAT(DATE_ADD( CURRENT_DATE, INTERVAL `n`.`n` + 7 DAY),"%Y-%m-%d")
    ELSE NULL
   END
FROM (
SELECT
  ((`hi`.`n` << 4) | `lo`.`n`) AS `n`
FROM (`number_generator_16` `lo`
   JOIN `number_generator_16` `hi`)
) `n`
WHERE n.n <100
;
/*
review test data
SELECT * FROM a_testdatestdate;

Create a view to handle your logic around dates and NULL values
*/
DROP VIEW IF EXISTS v_testdatestdate;
CREATE OR REPLACE VIEW v_testdatestdate AS SELECT
        n, 
        tdate, 
        CASE 
            WHEN  ISNULL(tigx) AND  ISNULL(tclosed) AND  ISNULL(tcompleted) THEN CURRENT_DATE
            WHEN NOT ISNULL(tigx) AND NOT ISNULL(tclosed) AND NOT ISNULL(tcompleted) THEN `tclosed`
            ELSE LEAST(IFNULL(tigx, CURRENT_DATE), IFNULL(tclosed, CURRENT_DATE), IFNULL(tcompleted, CURRENT_DATE))
        END AS dte
        FROM a_testdatestdate;  
/*
Then generate your averages from a statement like this
I have left the statement in this state so you can unpick it to suit your requirements
*/
SELECT 
ROUND(AVG(`DateDiff`),1)
FROM
(
    SELECT
    DATEDIFF(dte, tdate) AS `DateDiff`
    FROM v_testdatestdate V
) B
;

--> Result = 57.9 in this case.