How can i avoid duplication while joining two tables - mysql

i have two tables
1. test 1
2. test 2
First table has
**id** - **name**
1 - kerala
2 - Tamilnadu
Second table
**name** - **jid**
value 1 - 1
value 2 - 1
value 3 - 1
value 4 - 1
value 5 - 2
My Query --
SELECT t1.name, t2.name
FROM test1 t1
INNER JOIN test2 t2
WHERE t1.id = t2.jid
now i get this result
**name** - **name**
Kerala - value 1
kerala - value 2
kerala - value 3
kerala - value 4
But i need a result like this
Kerala - value 1
- value 2
- value 3
- value 4
the value ' Kerala ' should not be repeated .

you can user Group concat method.Pls check below query
SELECT t1.name,GROUP_CONCAT(t2.name) FROM test1 t1 INNER JOIN test2 t2 WHERE t1.id = t2.jid

You can use the following query:
SELECT CASE
WHEN t2.name = t3.firstName THEN t1.name
ELSE ''
END AS name,
t2.name
FROM test1 t1
INNER JOIN test2 t2 ON t1.id = t2.jid
INNER JOIN (
SELECT jid, MIN(name) AS firstName
FROM test2
GROUP BY jid) AS t3 ON t2.jid = t3.jid
This will produce the required result as long as there is a single record having MIN(name) per jid in test2 table.
Demo here

try this
SELECT IF (#oldname = name1,'',name1),
name2,
#oldname:=name1 AS oldname FROM
(
SELECT t1.name AS name1, t2.name AS name2
FROM test1 t1
INNER JOIN test2 t2
WHERE t1.id = t2.jid
) t,
(SELECT #oldname:='' ) tmp;

I don't think it's possible - you can't have empty values inside returned values.

Related

Select MAX of each corresponding row [duplicate]

This question already has answers here:
Retrieving the last record in each group - MySQL
(33 answers)
Closed 11 months ago.
new to SQL but I'll try to be clear,
I have 3 table, which have corresponding key columns. I need to select the row the MAX Value of a set column, for EACH of it's corresponding column.
Table1
ID1 Value1
1 Marie
2 Max
3 John
Table2
ID2 Value2
1 First
2 Second
3 Third
Table3
ID1 ID2
1 1
1 2
2 1
2 2
2 3
3 1
So far I have something like so;
SELECT T1.Value1, T2.Value2 FROM Table1 T1
INNER JOIN Table3 T3 ON T1.ID1 = T3.ID1
INNER JOIN Table2 T2 ON T3.ID2 = T2.ID1
WHERE (That's where I can't formulate correctly)
So far my tables are correctly joined, but I want to output only the rows where ID2 is at it's max value for the corresponding ID1.
So we'd have
ID1 ID2
1 2
2 3
3 3
And so, from correspondence of value we'd finally have.
Value1 Value2
Marie Second
Max Third
John First
Any help? Also, group by is prohibited.
You must use MAX in WHERE condition:
SELECT
T1.Value1,
T2.Value2
FROM
Table1 T1
INNER JOIN Table3 T3 ON T1.ID1 = T3.ID1
INNER JOIN Table2 T2 ON T3.ID2 = T2.ID1
WHERE
T3.ID2 = (
SELECT
MAX(T3_alias.ID2)
FROM
Table3 AS T3_alias
WHERE
T3_alias.ID1 = T1.ID1
)

SQL select rows with number in sequence

I have 1:N table where every entity may have asigned multiple numbers.
ID Number
1 10
1 13
1 11
1 12
1 16
2 11
2 12
2 13
2 10
Now,I want all IDs which have for example 3 numbers in ascending sequence. I do not specify which numbers I want, I just want the SQL to return me all possible combinations it can find but the numbers has to be in ascending sequence and the sequence must contain exactly 3 numbers. The numbers are allways integers of any value. The numbers in result have to be next to each other (12,13,16)is not valid result.
For 3 numbers in this example it would be :
ID 1 : (10,11,12),(11,12,13)
ID 2 : (11,12,13),(10,11,13)
For 2 numbers in this example it would be:
ID 1 : (10,11),(11,12),(12,13)
ID 2 : (11,12)(12,13)
Is this possible in SQL select? Thanx
A solution whats comes close to your expected output.
Involves using self inner joins incombination with CONCAT_WS, GROUP_CONCAT..
For group of three you use this query
Query
SET SESSION group_concat_max_len = ##max_allowed_packet
SELECT
records.ID
, GROUP_CONCAT(CONCAT('(', records.number, ')'))
FROM (
SELECT
DISTINCT
table11.ID
, CONCAT_WS(
','
, table11.Number
, table12.Number
, table13.Number
) AS number
FROM
Table1 AS table11
INNER JOIN
Table1 AS table12
ON
table11.Number + 1 = table12.Number
INNER JOIN
Table1 table13
ON
table12.Number + 1 = table13.Number
ORDER BY
table11.ID ASC
, table11.Number ASC
) AS records
GROUP BY
records.ID
Result
| ID | GROUP_CONCAT(CONCAT('(', records.number, ')')) |
|----|------------------------------------------------|
| 1 | (11,12,13),(10,11,12) |
| 2 | (11,12,13),(10,11,12) |
see demo http://sqlfiddle.com/#!9/c5dfce/39
Simply use join. This produces a result set with each examples of sequential numbers on a different row:
select id, t1.number, t2.number, t3.number
from t t1 join
t t2
on t2.id = t1.id and t2.number = t1.number + 1 join
t t3
on t3.id = t2.id and t3.number = t2.number + 1;
If you really wanted a list, you would simply do:
select id,
group_concat('(', t1.number, ',', t2.number, ',', t3.number, ')') as groups
from t t1 join
t t2
on t2.id = t1.id and t2.number = t1.number + 1 join
t t3
on t3.id = t2.id and t3.number = t2.number + 1
group by t1.id;

SQL Combining data from 3 tables to from a 4th table based on some conditions

I have 3 tables:-
table1 :-
ReportType | ResourceId
t2 123
t3 5
table2:-
Id | Name | Created
1 A 10
2 B 11
123 C 12
table3:-
Id | Name | Created
4 D 13
5 E 14
6 F 15
table1's ResourceId and table2 and 3's Id column have same values
I want to create a 4th table like this:-
ReportType | ResourceId | Name | Created
t2 123 C 12
t3 5 E 14
such that wherever table1's ReportType is t2 I want the Name and Created value from table2 for the condition table1.ResourceId = table2.Id and wherever table1's ResourceType is t3 I want the Name and Created value from table3 for the condition table1.ResourceId = table3.Id.
PS: This isn't some sort of HomeWork. I have been stuck at this query for the past 1 hour, I have read various answers and tried a few queries of my own before posting the question. Any help would really be appreciated.
Explanation in comments :)
--here we join first and second table, but we filter results to include only ReportType = t2
select t1.ReportType, t1.ResourceId, t2.Name, t2.Created from table1 as t1 join table2 as t2 on t1.ResourceId = t2.id
where t1.ReportType = 't2'
union all
--here we join first and third table, but we filter results to include only ReportType = t3
select t1.ReportType, t1.ResourceId, t3.Name, t3.Created from table1 as t1 join table3 as t3 on t1.ResourceId = t3.id
where t1.ReportType = 't3'
You can use the below query:
select report_type, resourceid,name, created from dbo.t2, dbo.t1
where report_type='t2' and ResourceId=id
UNION
select report_type, resourceid,name, created from dbo.t3, dbo.t1
where report_type='t3' and ResourceId=id;

Mixing 3 sql queries in 1

I have 3 tables as follows
Table1
Id Name
1 abcd
2 bcd
3 dabc
Table2
Id2 Name2
2 xyz
3 def
4 mno
Table3
Id Id2 Value
1 4 1
2 3 1
3 4 1
Now,
From table1 : I have to select all Id where Name is %abc%
From table2: I have to select Id2 where Name2 is "mno"
From Table3: I have to change value to 0 from 1 where Id's value are from Table1 and Id2 is from Table2.
Table 1:
select Id from Table1 where Name like '%abc%'
Table2 :
select Id2 from Table2 where Name2 = "mno"
Table 3:
update Table3 set Value = 0 where Id in() and Id2=
But, I dont know how to make it 1 single query. Can anyone please guide me up ?
Refer to: prior stack article
You've not explained how T1 relates to T2, So I have assumed a cross join.
Whenever you have a record in T1 with name like '%abc%' (1,3) in your data..
and whenever you have a record in T2 with a name equal to 'mno' 4 then you want the value in table 3 to be 0
so the select we generate should produce
1,4
3,4
and when we inner join this back to table 3 it only selects
Id Id2 Value
1 4 1
3 4 1
Now we generate an update based on this select as outlined in the link provided above...
UPDATE table3
INNER JOIN (
SSELECT t1.ID t1ID, t2.id t2ID
FROM table1 t1
CROSS JOIN table2
WHERE t1.name like '%abc%'
and t2.name like = 'mno') B
on B.t1ID = t3.Id
and B.t2ID = T3.ID2
SET value = 0
Giving us a result of
Id Id2 Value
1 4 0
2 3 1
3 4 0
if we select * from table3
update t3
set t3.Value = 0
from Table3 t3
inner join Table1 t1
on t3.Id = t1.Id
inner join Table2 t2
on t3.Id2 = t2.Id2
where t1.Name like '%abc%' and t2.Name2 = 'mno'
OR
update Table3
set value = 0
where Id in (select Id from Table1 where Name like '%abc%')
and Id2 in (select Id2 from Table2 where Name2 = 'mno')
You should think about UPDATE ... WHERE EXISTS as follows:
update Table3 set Value = 0
WHERE EXISTS (SELECT 1 FROM Table1 where Name LIKE '%abc%' AND Table1.Id=Table3.Id )
AND EXISTS (SELECT 1 FROM Table2 where Name2 = "mno" AND Table2.Id2=Table3.Id2)

Mysql update max value with group by

I have a simple table that has many rows already:
id grade ...
1 1 ...
2 2 ...
3 2 ...
4 1 ...
5 1 ...
Now i want to add a column "relative_order", which is the order in that grade. So the table becomes:
id grade ... relative_order
1 1 ... 1
2 2 ... 1
3 2 ... 2
4 1 ... 2
5 1 ... 3
After i add the column, all the relative_order becomes 0 first. How can i fill the relative_order column using update syntax?
I tried using inner join, but failed:
UPDATE table AS i
INNER JOIN(
SELECT max(relative_order) as mOrder,grade
FROM table
GROUP BY grade
) AS j
ON i.grade = j.grade
SET i.relative_order = j.mOrder + 1
You could use this SELECT query that will return the relative_order that you need:
SELECT
t1.id,
t1.grade,
COUNT(t2.id) relative_order
FROM
yourtable t1 INNER JOIN yourtable t2
ON t1.grade=t2.grade AND t1.id>=t2.id
GROUP BY
t1.id,
t1.grade
or if you want to update the value, you can join your table with the previous query, like this:
UPDATE
yourtable INNER JOIN (
SELECT
t1.id,
t1.grade,
COUNT(t2.id) relative_order
FROM
yourtable t1 INNER JOIN yourtable t2
ON t1.grade=t2.grade AND t1.id>=t2.id
GROUP BY
t1.id,
t1.grade) seq
ON yourtable.id=seq.id AND yourtable.grade=seq.grade
SET
yourtable.relative_order = seq.relative_order
Please see fiddle here.