Count Consecutive Numeric values in SQL

问题

There are already many existing questions about this scenario, however I am unable to replicate the answers in my scenario.

I have a following sample Data Set:

ID Number  | Values 
754321       0
754321       0
754321       0
754321       0
754321       1
754321       0
754321       1
754321       0
754321       2
754321       0
754329       3
754329       4
754329       5
754329       6
754329       7
754329       8
754329       9

I want the SQL query that outputs the ID Number with the number of times the value of "0" appears consecutively. So, for the above table I would like to get the output as follows:

ID Number  Count of Consecutive 0 Values
754321     4

回答1:

This is a form of gaps-and-islands problem. You can assign each 0 a group by counting the number of non-zero values before it. Then aggregate.

However, SQL tables represent unordered sets. There is no ordering unless a column specifies the ordering. Let me assume you have one. Then:

select count(*)
from (select t.*,
             sum(values <> 0) over (partition by idnumber order by <ordering col>) as grp
      from t
     ) t
where values = 0
group by idnumber, grp;

回答2:

If you're running a version of MySQL that doesn't support window functions, you can implement this functionality using variables:

SELECT `ID Number`, MAX(cnt) AS `Max Consecutive 0 Values`
FROM (SELECT `ID Number`, SUM(`Values` = 0) AS cnt
      FROM (SELECT `ID Number`, `Values`,
                   @cnz:= CASE WHEN `Values` != 0 THEN @cnz + 1
                               ELSE @cnz
                          END AS cnz
            FROM data
            CROSS JOIN (SELECT @cnz := 0) init
            ORDER BY date
            ) c
      GROUP BY `ID Number`, cnz) s
GROUP BY `ID Number`

Output

ID Number   Max Consecutive 0 Values
754321      4
754329      0

Demo on SQLFiddle

来源：https://stackoverflow.com/questions/59760157/count-consecutive-numeric-values-in-sql

标签

mysql

sql

gaps-and-islands