Solved

# How to check sequence missing in postgress

Posted on 2014-12-03
174 Views
Hi,

I have a table in PostgreSQL that the datatype of the field is (character varying(255) for some reason now I need to check this across all records if there is any sequence is missing, if any sequence is missing what are those sequences..

sample data

``````12345
12346
12347
12348
12350
12351
12356
``````

and what I want is
``````12349
12352
12353
12354
12355
``````

and PostgreSQL version is 9.3 regards
0
Question by:hi4ppl
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LVL 11

Expert Comment

ID: 40479665
This solution determines which key (myfield) has missing sequential value(s) after it, and how many are missing after that key:
``````create table mytable
( myfield int
);

insert into mytable values (12345);
insert into mytable values (12346);
insert into mytable values (12347);
insert into mytable values (12348);
insert into mytable values (12350);
insert into mytable values (12351);
insert into mytable values (12356);

WITH sortedData as
(	SELECT	row_number() OVER (ORDER BY myfield) as rn
,	myfield
FROM	mytable
)
SELECT	a.myfield
,	b.myfield - a.myfield - 1 as missing_keys
FROM	sortedData a
JOIN	sortedData b	ON	a.rn = b.rn - 1
WHERE	b.myfield - a.myfield > 1

MYFIELD	MISSING_KEYS
------- ------------
12348	1
12351	4
``````
0

LVL 1

Author Comment

ID: 40480437
Hi,

thanks, but my data field is character and this didn't work for that, can you suggest how to convert that and put it in this query?

regards
0

LVL 32

Expert Comment

ID: 40480606
Determine the lowest and highest numeric values of your field -
select min(num) as start, max(num) as stop from
(select to_number(yourfield,'99999') as num  ==> using format mask to accommodate highest value
from yourtable)

Then
select * from generate_series(start,stop)  ==> substituting values for start and stop from previous query
except
select to_number(yourfield,'99999') from yourtable
0

LVL 25

Expert Comment

ID: 40486357
Hi!

Try this query

``````WITH seq_max AS (
SELECT max(yourvarcharfield) FROM yourtable
),
seq_min AS (
SELECT min(yourvarcharfield) FROM yourtable
)
SELECT * FROM generate_series((SELECT min FROM seq_min),(SELECT max FROM seq_max))
EXCEPT
SELECT yourvarcharfield FROM yourtable
``````
Note that this query can be performance intensive on large tables.

Regards,
Tomas Helgi
0

LVL 11

Accepted Solution

John_Vidmar earned 500 total points
ID: 40487792
Same solution as I posted previously, this time the key-field is varchar(255) instead of integer:
``````create table mytable
( myfield varchar(255)
);

insert into mytable values ('12345');
insert into mytable values ('12346');
insert into mytable values ('12347');
insert into mytable values ('12348');
insert into mytable values ('12350');
insert into mytable values ('12351');
insert into mytable values ('12356');

WITH sortedData as
(	SELECT	row_number() OVER (ORDER BY myfield) as rn
,	CAST(myfield as int) as myfield
FROM	mytable
)
SELECT	a.myfield
,	b.myfield - a.myfield - 1 as missing_keys
FROM	sortedData a
JOIN	sortedData b	ON	a.rn = b.rn - 1
WHERE	b.myfield - a.myfield > 1

MYFIELD	MISSING_KEYS
------- ------------
12348	1
12351	4
``````
0

LVL 32

Expert Comment

ID: 40489139
The asker seems to want the missing values in the series, not the number of missing values. The following should return the missing values as character date:
with cte as
(select min(to_number(yourfield,'99999')) as start, max(to_number(yourfield,'99999')) as stop
from yourtable)
select to_char(g.num,'99999')
from generate_series(cte.start,cte.stop) as g(num)
left join yourtable y on y.yourfield = to_char(g.num,'99999')
where y.yourfield is null;
0

LVL 32

Expert Comment

ID: 40489143
typo - as character data (not date)
0

LVL 22

Expert Comment

ID: 40507154
select generate_series( col_name::integer + 1, alias_1::integer - 1 ) from
( select col_name,
lead(col_name) over( order by col_name) as alias_1
from tt ) as foo
where alias_1 <> (col_name::integer+1)::text;

generate_series
-----------------
12349
12352
12353
12354
12355
(5 rows)
0

LVL 32

Expert Comment

ID: 40513034
and what I want is

12349
12352
12353
12354
12355
1:
and what accepted solution provides is
MYFIELD      MISSING_KEYS
------- ------------
12348      1
12351      4

???
0

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