I want to get largest location id of label.
But, It is very slow on follow query.
agens=# match (n:v) return max(graphid_locid(id(n)));
max
-----
6
(1 row)
How to get max location id of label more faster on AgensGraph?
Fetch related sequence value from pg_sequences table.
agens=# select start_value from pg_sequences where schemaname = 'graph' and sequencename = 'v_id_seq';
start_value
-------------
6
(1 row)
Related
I'm storing arrays of integers as json in a mariadb (10.3.23) table :
SELECT
tag_list
FROM
dw.final_document
LIMIT 1 ;
Result :
[903, 1258, 1261, 393]
To retrieve entries matching a specific id, this works :
SELECT SQL_NO_CACHE
count(*)
FROM
dw.final_document
where
JSON_CONTAINS(tag_list, 684 ) ;
Result :
+----------+
| count(*) |
+----------+
| 9696 |
+----------+
1 row in set (2.084 sec)
However the performance is not good without an index (2 sec in a 1M rows table)
The possibility to index a specific field of the json is well documented (percona post).
You can add an index on a generated column like this :
ALTER TABLE test_features
ADD COLUMN street VARCHAR(30)
GENERATED ALWAYS AS (json_unquote(json_extract(`feature`,'$.properties.STREET'))) VIRTUAL;
Is there a similar way to index arrays of integers ?
I have a stored procedure which selects columns from multiple tables.
what i want is to be able to get the number of rows with values Y and number or row if value N that are in the returned records.
Example
name availableYN
john y
gary n
mark y
I want to be able to have that result and also a count like
y 2
n 1
any guidance will be much appreciated.
Try using COUNT
SELECT
availableYN,
COUNT(availableYN) AS cnt
FROM
My_Table
GROUP BY
availableYN
I'm new to SQL Server so I apologize if my question seems too easy. I tried finding and answer on my own, but I'm failing miserably. I am trying to create a query which will return total size on the drive of each row in the table.
i thought about using dbcc showconting but it doesn't work for varchar(max) which appears in my table. Also, it doesn't return size for each row, but rather the average, max and min size. My reading so far suggests that it is not possible to get query that could show the size of each individual row in the table so I decided to settle for the total length of all characters in each column in each row. Indirectly it will give me idea about the size of each row.
I have a table with some varchar(500) and varchar(max) columns. I noticed that some of the rows are a lot bigger than others.
What I need is top 1000 longest rows in the table, preferably in an output showing two columns:
Column 1 showing EntryID
Column 2 showing total length of the characters in all columns together for that record (eg total length of the characters in the column 1 + total length of the characters in the column 2 + column3 + column4 etc...) It would be great if this could be aliased RowLength.
What I tried so far is:
SELECT TOP 1000
(LEN(columnname1) + LEN(columnname2) + LEN(columnname3) + LEN(columnname4)) as RowLength,
FROM dbo.tablename
ORDER BY Length Desc
It works, but it doesn't show entry ID corresponding to the total length of all characters in the row. How do I add it?
It also doesn't show the alias for the column showing number of characters in the row.
Could you please suggest how I can change the query to get the expected outcome? I'll be very grateful for any suggestions.
it doesn't show EntryID corresponding to the total length of all
characters in the row. It also doesn't show the alias for the column
showing number of characters in the row.
You have not specified an alias, so what should it show? You also haven't selected EntryID. If you want the longest 1000 rows you have to order by the length:
SELECT TOP 1000
EntryID,
Length = LEN(columnname1) + LEN(columnname2) + LEN(columnname3) + LEN(columnname4)
FROM dbo.tablename
ORDER BY Length DESC
SELECT TOP 1000 EntryID,
(LEN(columnname1) + LEN(columnname2) + LEN(columnname3) + LEN(columnname4)) AS RowLength,
FROM dbo.tablename
ORDER BY EntryID
I am using PostgreSQL and let's say I have a tasks table to keep track of task items. Tasks table is as follows;
Id Name Index
7 name A 1
5 name B 2
6 name C 3
3 name D 4
Index column in tasks table stores the sort order of the tasks. Therefore I will output the tasks with respect to index in increasing order.
So When I change Task D(id = 3)' s index into 2 the new indexes should be as below;
Id Name Index
7 name A 1
5 name B 3
6 name C 4
3 name D 2
or when I change Task A(id = 7)' s index into 4 the new indexes should be as below;
Id Name Index
7 name A 4
5 name B 2
6 name C 3
3 name D 1
What I think is updating all row's index values one by one is pretty inefficient.
So what is the most efficient way to update all index values when I change one of the indexes in my Tasks table?
Edit :
First of all sorry for the confusion. What I am asking is not a simple exchanging two row indexes. If you look at the examples when I change Task D's index in to 2 more than one rows change. So when Task D is 2, Task B becomes 3 and Task C becomes 4.
For instance;
It is like when you drag Task D and drop below Task A so that it's index becomes 2 and B and C's index increases by 1.
SQL Fiddle
What you are doing is exchanging two row's indexes. So it is necessary to store the index value of the first updated one in a temp variable and setting it temporarily to a special value to avoid a unique index collision, that is, if the index is unique. If the index is not unique that step is unnecessary.
begin;
create temp table t as
select
(
select index
from tasks
where id = 3
) as index,
(
select id
from tasks
where index = 2
) as id
;
update tasks
set index = -1
where id = (select id from t)
;
update tasks
set index = 2
where id = 3
;
update tasks
set index = (select index from t)
where id = (select id from t)
;
drop table t;
commit;
The following assumes the index column (as well as id) is unique:
with swapped as (
select n1.id as id1,
n1.name as name1,
n1.index as index1,
n2.id as id2,
n2.name as name2,
n2.index as index2
from names n1
join names n2 on n2.index = 2 -- this is the value of the "new index"
where n1.id = 3 -- this is the id of the row where the index should be changed to the new value
)
update names as n
set index = case
when n.id = s.id1 then s.index2
when n.id = s.id2 then s.index1
end
from swapped s
where n.id in (s.id1, s.id2);
The CTE first creates a single row with the ids of the two rows to be swapped and then the update just compares the ids of the target table with those from the CTE, swapping the values.
SQLFiddle example: http://sqlfiddle.com/#!15/71dc2/1
The data in the table looks like this
ID Value
1 5006049
2 5006050
How do I select a substring so that I get
R6049
R6050
Keeping in mind that the values are sequential starting from
5000001 = R1
to
5999999 = R999999
Just substract
SELECT 'R' + CAST(VALUE - 5000000 as VARCHAR(6))
FROM table
SqlFiddle
I think as easily as this:
Select 'R'+Substring(convert(VARCHAR(7), Value), 4,7)
Which will give R0001 (do you want the zeros?)
If you don't want the zeros / only looking to remove the top digit:
Select 'R'+ convert(VARCHAR(6),Value - 5000000)