I have several tables with a bunch of fields and I need a Query that includes ALL the fields from two tables (JOINs). The result should have consistent naming scheme for the fields, that survives when I add fields to the source table.
To always select all fields of a table I can use the * operator. But when I join two tables using the *, it prepends the fields that occur in both tables (and only those) with the table name.
SELECT kids.*, parents.* FROM parents INNER JOIN kids ON parents.ID = kids.ParentID;
gives me
kids.name, birthday, school, parents.name, address ...
When I add a birthday column to the parents table I get
kids.name, kids.birthday, school, parents.name, parents.birthday, address ...
And I have to update birthday to kids.birthday everywhere.
Is there a way to prepend all column names in the beginning?
So I'd get
kids.name, kids.birthday, kids.school, parents.name, parents.address ...
in the first place?
Related
I have two tables of world countries Independence Day and I wanted to combine them into one table with a distinct id, but they are using different Primary keys, any suggestions will be appreciated.
Summary of request: How to combine two tables with different Primary Keys but the other fields in common and removing duplicate fields ideally Hash Match and removing duplicates
Expected Results this will include all the unique countries in both tables, please one table may have more countries and we want to make sure we take all the distinct countries from each table. Ideally, the solution will be likely to be of like Hash Match operator in SQL which implements several different logical operations that all use an in-memory hash table for finding matching data. Many thanks in advance
The image of two tables which needs combining.
You seem to want full join:
select a.*, b.* -- select the columns you want
from a full join
b
on a.country = b.country;
If you want to assign a new unique id use row_number():
select row_number() over (order by coalesce(a.country, b.country)) as new_id,
a.*, b.* -- select the columns you want
from a full join
b
on a.country = b.country;
I am working on ABAP program - user input is to query column ANLAGE and output is to get all records from table EADZ (and only fields of EADZ) based on ANLAGE.
Statement and joins should work like this:
Input ANLAGE, find in table EASTL, gets LOGIKNR
Input LOGIKNR, find in table EGERR, gets EQUNR
Input EQUNR, find in table ETDZ, gets LOGIKZW
Input LOGIKZW, find in table EADZ, gets all records (this is the final output)
Here is the code I tried:
DATA: gt_cas_rezy TYPE STANDARD TABLE OF eadz,
lv_dummy_eanl LIKE eanl-anlage.
SELECT-OPTIONS: so_anl FOR lv_dummy_eanl NO INTERVALS NO-EXTENSION.
SELECT * FROM eadz
INNER JOIN etdz ON eadz~logikzw EQ etdz~logikzw
INNER JOIN egerr ON etdz~equnr EQ egerr~equnr
INNER JOIN eastl ON egerr~logiknr EQ eastl~logiknr
INTO CORRESPONDING FIELDS OF TABLE #gt_cas_rezy
WHERE eastl~anlage IN #so_anl.
I got the records from table EADZ except that the date fields are empty (even though, they are filled in database table). I am assuming there is a problem with JOINs since in statement like this I join all the fields of all 4 tables into one "record" and then to corresponding fields of internal table.
How to get the values of date fields?
You can find the answer in the documentation.
If a column name appears multiple times and no alternative column name was granted, the last column listed is assigned.
In your case, at least two tables share the same column name. Therefore the values from the last mentioned table are used in the join.
You can solve this by listing the columns explicitly (or eadz~* in your case), giving an alias if required.
SELECT EADZ~* FROM EADZ INNER JOIN ETDZ ON EADZ~LOGIKZW = ETDZ~LOGIKZW
INNER JOIN EGERR ON ETDZ~EQUNR = EGERR~EQUNR
INNER JOIN EASTL ON EGERR~LOGIKNR = EASTL~LOGIKNR
INTO CORRESPONDING FIELDS OF TABLE #gt_cas_rezy
WHERE EASTL~ANLAGE IN #SO_ANL.
If you require additional fields, you can add them explicily with e.g. EADZ~*, EASTL~A.
So I have three tables: companies, addresses and company_address.
For optimization reasons I need to copy city column from addresses table to companies table. Relation between companies and addresses is many to one (as many companies can occupy same address). They are connected through company_address table, consisting of address_id and company_id columns.
I found this solution for case without intermediate table: How to copy one column of a table into another table's column in PostgreSQL comparing same ID
Trying to modify query I came up with:
UPDATE company SET company.city=foo.city
FROM (
SELECT company_address.company_id, company_address.address_id, address.city
FROM address LEFT JOIN company_address
ON address.id=company_address.address_id
) foo
WHERE company.id=foo.company_id;
but it gives error:
ERROR: column "company" of relation "company" does not exist
I cant figure out what is going on. I'll be grateful for any ideas.
You don't need a subquery for that. Also, refer in the SET clause to your table columns without preceding with table name.
I believe that since your WHERE condition includes joined table, it should be INNER JOIN instead of a LEFT JOIN.
UPDATE company c
SET city = a.city
FROM address a
INNER JOIN company_address ca ON a.id = ca.address_id
WHERE c.id = ca.company_id
Note how using aliases for table names shortens the code and makes it readable at the very first glance.
You're right syntactically, you just don't need the table name at the beginning of the update statement:
UPDATE company SET city=foo.city
FROM (
SELECT company_address.company_id, company_address.address_id, address.city
FROM address LEFT JOIN company_address
ON address.id=company_address.address_id
) foo
WHERE company.id=foo.company_id;
I have two tables: one called EMP_Names which simply stores ID and Employee_Name and another table called EMP_Main which stores the main data and which refers to EMP_Names via IDs. Amongst other fields EMP_Main has fields called Technician_Name_ID and Leader_Name_ID which is related to EMP_Names. My problem is this: how can i run a query where both Technician_Name_ID and Leader_Name_ID resolve to Names? In other words both ID fields refer to the same EMP_Names.ID but I can only establish one relationship between the two tables.
Don't know if I'm clear because it's difficult to explain ...
You can use join but you need multiple joins.
select em.*, ent.name as technician, enl.name as leader
from (emp_main as em left join
emp_names as ent
on em.technician_name_id = ent.id
) left join
emp_names as enl
on em.leader_name_id = enl.id;
These are left joins in case the fields are not populated for all rows.
In my tables I have for example
CountyID,County and CityID in the county table and in the city table I have table I have for example
City ID and City
How do I create a report that pulls the County from the county table and pulls city based upon the cityid in the county table.
Thanks
Since this is quite a basic question, I'll give you a basic answer instead of the code to do it for you.
Where tables have columns that "match" each other, you can join them together on what they have in common, and query the result almost as if it was one table.
There are also different types of join based on what you want - for example it might be that some rows in one of the tables you're joining together don't have a corresponding match.
If you're sure that a city will definitely have a corresponding county, try inner joining the two tables on their matching column CityID and querying the result.
The obvious common link between both tables is CityID, so you'd be joining on that. I think you have the data organized wrong though, I'd put CountryID in the City table rather than CityID in the country table. Then, based on the CountryID selected, you can limit your query of the City table based on that.
To follow in context of Bridge's answer, you are obviously new to SQL and there are many places to dig up how to write them. However, the most fundamental basics you should train yourself with is always apply the table name or alias to prevent ambiguity and try to avoid using column names that might be considered reserved words to the language... they always appear to bite people.
That said, the most basic of queries is
select
T1.field1,
T1.field2,
etc with more fields you want
from
FirstTable as T1
where
(some conditional criteria)
order by
(some column or columns)
Now, when dealing with multiple tables, you need the JOINs... typically INNER or LEFT are most common. Inner means MUST match in both tables. LEFT means must match the table on the left side regardless of a match to the right... ex:
select
T1.Field1,
T2.SomeField,
T3.MaybeExistsField
from
SomeTable T1
Join SecondTable T2
on T1.SomeKey = T2.MatchingColumnInSecondTable
LEFT JOIN ThirdTable T3
on T1.AnotherKey = T3.ColumnThatMayHaveTheMatchingKey
order by
T2.SomeField DESC,
T1.Field1
From these examples, you should easily be able to incorporate your tables and their relationships to each other into your results...