What is the most efficient way to get data from two tables set up in the following way:
Table 1:
ID(PK) | Name | Age
--------------------------
1 | Jim | 44
2 | Jane | 35
3 | John | 22
Table 2
Name(PK) | Pet(PK)
-----------------
Jim | Cat
Jim | Dog
Jane | Fish
There is a constraint on "Name" with the FK in Table 2
Results
I want the age and all the pets for a specific person.
Name | Age | Pet
---------------------
Jim | 44 | Cat
Jim | 44 | Dog
As I see it these are my options:
1) Left join table 2 on Name and end up with redundant data in my resulting array for Name and Age (as above).
2) Use a function that turns the pets into a comma separated list.
3) Use 2 separate selects.
My question is relating to performance of the 3 options above. I don't need SQL (specifically, unless you want to suggest another method).
Thanks!
select
tb01.name, tb01.age, tb02.pet
from
table01 tb01
left join table02 tb02 on tb02.name = tb01.name
Related
EDIT
I've edited this question to make it a little more concise, if you see my edit history you will see my effort and 'what I've tried' but it was adding a lot of unnecessary noise and causing confusion so here is a summary of input and output:
People:
ID | FullName
--------------------
1 | Jimmy
2 | John
3 | Becky
PeopleJobRequirements:
ID | PersonId | Title
--------------------
1 | 1 | Some Requirement
2 | 1 | Another Requirement
3 | 2 | Some Requirement
4 | 3 | Another Requirement
Output:
FullName | RequirementTitle
---------------------------
Jimmy | Some Requirement
Jimmy | Another Requirement
John | Some Requirement
John | null
Becky | null
Becky | Another Requirement
Each person has 2 records, because that's how many distinct requirements there are in the table (distinct based on 'Title').
Assume there is no third table - the 'PeopleJobRequirements' is unique to each person (one person to many requirements), but there will be duplicate Titles in there (some people have the same job requirements).
Sincere apologies for any confusion caused by the recent updates.
CROSS JOIN to get equal record for each person and LEFT JOIN for matching records.
Following query should work in your scenario
select p.Id, p.FullName,r.Title
FROM People p
cross join (select distinct title from PeopleJobRequirements ) pj
left join PeopleJobRequirements r on p.id=r.personid and pj.Title=r.Title
order by fullname
Online Demo
Output
+----+----------+---------------------+
| Id | FullName | Title |
+----+----------+---------------------+
| 3 | Becky | Another Requirement |
+----+----------+---------------------+
| 3 | Becky | NULL |
+----+----------+---------------------+
| 1 | Jimmy | Some Requirement |
+----+----------+---------------------+
| 1 | Jimmy | Another Requirement |
+----+----------+---------------------+
| 2 | John | NULL |
+----+----------+---------------------+
| 2 | John | Some Requirement |
+----+----------+---------------------+
use left join, no need any subquery
select p.*,jr.*,jrr.*
from People p left join
PeopleJobRequirements jr on p.Id=jrPersonId
left join JobRoleRequirements jrr p.id=jrr.PersonId
according the explanation, People and PeopleJobRequirements tables have many to many relationship (n to n).
so first of all you'll need another table to relate these to table.
first do this and then a full join will make it right.
I'm pretty new to SQL Server (using ssms). I need some help to insert and organize data from one table into multiple tables (which are connected to each other by PK/FK).
The source table has the following columns:
Email, UserName, Phone
It's a messy table with lots of duplicates: same email with different username and so on..
My data tables are:
Person - PersonID(PK, int, not null)
Email - Email (nvarchar, null) , PersonID (FK, int, not null)
Phone - PhoneNumber (int, null) , PersonID (FK, int, not null)
UserName - UserName (nvarchar, null) , PersonID (FK, int, not null)
For each row in the source table, I need to check if the person already exists (by Email); if it does exist, I need to add the new data (if any), else I need to create a new person and add the data.
I searched here for some solutions and find recommendations of using CURSOR.
I tried it, but it takes a really long time to execute (hours.. and still going)
Thanks for any help!
example:
from>
EMAIL | USERNAME | PHONE
------------------------
a#a.a | john | 956165
b#b.b | smith | 123456
c#c.c | bob | 654321
d#d.d | mike | 986514
a#a.a | dan | 658732
e#e.e | dave | 147258
f#f.f | harry | 951962
b#b.b | emmy | 456789
g#g.g | kelly | 789466
h#h.h | kelly | 258369
a#a.a | ana | 852369
to>
EMAIL | PERSONID
----------------
a#a.a | 1
b#b.b | 2
c#c.c | 3
d#d.d | 4
e#e.e | 5
f#f.f | 6
g#g.g | 7
h#h.h | 8
USERNAME | PERSONID
-------------------
john | 1
smith | 2
bob | 3
mike | 4
dan | 1
dave | 5
harry | 6
emmy | 2
kelly | 7
kelly | 8
ana | 1
PHONE | PERSONID
----------------
956165 | 1
123456 | 2
654321 | 3
986514 | 4
658732 | 1
147258 | 5
951962 | 6
456789 | 2
789466 | 7
258369 | 8
852369 | 1
Cursors will generally be slower as they operate on a row-by-row basis. Using set based operations, such as a join, will yield better performance. It's somewhat older, but this article further details the implications of cursors as opposed to set operations. I wasn't entirely sure what columns you want to use to verify matches, as well as what data to add, but a basic example is below and you can fill in the columns as necessary. The Email table was used in the example. For the UPDATE, this will update existing rows based off corresponding rows in the source table. Being an INNER JOIN, only rows with matches on both sides will be impacted. In the second statement, this is an INSERT using only rows from the source table that don't exist in the Email table. This same functionality could also be accomplished using the MERGE statement, however there are a number of issues with this, including problems with deadlocks and key violations.
Update Existing Rows:
UPDATE E
SET E.ColumnA = SRC.ColumnA,
E.ColumnB = SRC.ColumnB
FROM YourDatabase.YourSchema.Email E
INNER JOIN YourDatabase.YourSchema.SourceTable SRC
ON E.Email = SRC.Email
Add New Rows:
INSERT INTO YourDatabase.YourSchema.Email (ColumnA, ColumnB)
SELECT
ColumnA,
ColumnB
FROM YourDatabase.YourSchema.SourceTable
WHERE EMAIL NOT IN ((SELECT EMAIL FROM YourDatabase.YourSchema.Email))
I want to create a new table using the results from some queries. I might be looking at this the wrong way so please feel free to let me know. Because of this I will try to make this question simple without putting my code to match each employee number with each manager level column from table2
I have two tables, one has employee names and employee numbers example
table 1
+-------------+-----------+-------------+-------------+
| emplpyeenum | firstname | last name | location |
+-------------+-----------+-------------+-------------+
| 11 | joe | free | JE |
| 22 | jill | yoyo | XX |
| 33 | yoda | null | 9U |
+-------------+-----------+-------------+-------------+
and another table with employee numbers under each manager level so basically a hierarchy example
Table 2
+---------+----------+----------+
| manager | manager2 | manager3 |
+---------+----------+----------+
| 11 | 22 | 33 |
+---------+----------+----------+
I want to make a new table that will have the names besides the numbers, so for example but with employee number beside the names
+---------+--------+----------+
| level 1 | level2 | level3 |
+---------+--------+----------+
| jill | joe | yoda |
+---------+--------+----------+
How can I do this?
edit sorry guys I don't have permission to create a new table or view
Why not change your table2 to this?
+------------+----------+
| EmployeeId | ManagerId|
+------------+----------+
| 11 | NULL |
+------------+----------+
| 22 | 11 |
+------------+----------+
| 33 | 22 |
+------------+----------+
Then you can do what you want with the data. At least your data will be properly normalized. In your table2. What happen if employee 33 hire another employee below him? You will add another column?
Based on your available table, this should give you the result you want.
SELECT m1.firstname, m2.firstname, m3.firstname
FROM table2 t
LEFT JOIN table1 m1 ON m1.employeenum = t.manager
LEFT JOIN table1 m2 ON m2.employeenum = t.manager2
LEFT JOIN table1 m3 ON m3.employeenum = t.manager3
You can just do a basic create table, then do a insert select to that will fill the table the way you need it. All you have to do is replace the select statement that I provided with the one you used to create the levels table output.
create table Levels
(
level1 varchar(25),
level2 varchar(25),
level3 varchar(25)
)
insert into Levels(level1, level2, level3)
select * from tables --here you would put the select statement that you used to create the information. If you dont have this script then let me know
Here are the two tables i have: [all columns in both tables are of type "text"], Table name and the column names are in bold fonts.
Names
--------------------------------
Name | DoB | Team |
--------------------------------
Harry | 3/12/85 | England
Kevin | 8/07/86 | England
James | 5/05/89 | England
Scores
------------------------
ScoreName | Score
------------------------
James-1 | 120
Harry-1 | 30
Harry-2 | 40
James-2 | 56
End result i need is a table that has the following
NameScores
---------------------------------------------
Name | DoB | Team | ScoreData
---------------------------------------------
Harry | 3/12/85 | England | "{"ScoreName":"Harry-1", "Score":"30"}, {"ScoreName":"Harry-2", "Score":"40"}"
Kevin | 8/07/86 | England | null
James | 5/05/89 | England | "{"ScoreName":"James-1", "Score":"120"}, {"ScoreName":"James-2", "Score":"56"}"
I need to do this using a single SQL command which i will use to create a materialized view.
I have gotten as far as realising that it will involve a combination of string_agg, JOIN and JSON, but haven't been able to crack it fully. Please help :)
I don't think the join is tricky. The complication is building the JSON object:
select n.name, n.dob, n.team,
json_agg(json_build_object('ScoreName', s.name,
'Score', s.score)) as ScoreData
from names n left join
scores s
ons.name like concat(s.name, '-', '%')
group by n.name, n.dob, n.team;
Note: json_build_object() was introduced in Postgres 9.4.
EDIT:
I think you can add a case statement to get the simple NULL:
(case when s.name is null then NULL
else json_agg(json_build_object('ScoreName', s.name,
'Score', s.score))
end) as ScoreData
Use json_agg() with row_to_json() to aggregate scores data into a json value:
select n.*, json_agg(row_to_json(s)) "ScoreData"
from "Names" n
left join "Scores" s
on n."Name" = regexp_replace(s."ScoreName", '(.*)-.*', '\1')
group by 1, 2, 3;
Name | DoB | Team | ScoreData
-------+---------+---------+---------------------------------------------------------------------------
Harry | 3/12/85 | England | [{"ScoreName":"Harry-1","Score":30}, {"ScoreName":"Harry-2","Score":40}]
James | 5/05/89 | England | [{"ScoreName":"James-1","Score":120}, {"ScoreName":"James-2","Score":56}]
Kevin | 8/07/86 | England | [null]
(3 rows)
I am trying to create a query that lists records from table 1 along with a status based on corresponding records in table 2 that have null values in one or more of the fields. The problem I am running into is how to include records from table 1 which have no corresponding record in table 2.
In my example, I want to list the names of all students in tblStudent along with a field indicating the status of their schedule in tblStudentSchedule. If either course or teacher field in tblStudentSchedule is Null or no corresponding record in tblStudentSchedule is found then I want to display "Incomplete". Otherwise, I want to display "Complete".
desired result
Name | Schedule Status
-----------------------
Bob | Incomplete
Sally | Incomplete
Jane | Incomplete
Matt | Incomplete
Jim | Complete
I'm working in Access. I would post my query attempts but I think they would just confuse the issue. This is probably very basic but I am having a mental block trying to wrap my brain around this one.
tblStudent
studentID | studentName
-----------------------
1 | Bob
2 | Sally
3 | Jane
4 | Matt
5 | Jim
tblStudentSchedule
studentID | period | course | teacher
-------------------------------------
1 | 1 | math | Jones
1 | 2 | <null> | Watson
2 | 1 | reading| <null>
4 | 1 | <null> | Crick
5 | 1 | math | Jones
select s.studentName as Name
, iif(sum(iif(ss.course is null or ss.teacher is null, 1, 0)) = 0,
'Complete', 'Incomplete')
as [Schedule Status]
from tblStudent s
left join
tblStudentSchedule ss
on ss.studentID = s.studentID
group by
s.studentName
A left join returns a single row with null when a match is not found. So the check on ss.course is null will also trigger when the student is absent from the schedule table.
If no corresponding record in tblStudentSchedule is found, you can get rows from this table as null coulmns by using left or right joins. Read below:
http://office.microsoft.com/en-us/access-help/left-join-right-join-operations-HP001032251.aspx
And then to convert null column use isnull function
http://www.techonthenet.com/access/functions/advanced/isnull.php
Or use a case statement to check for null
http://www.techonthenet.com/access/functions/advanced/case.php