Is there a way in ABAP's OpenSQL to simplify the select columns in a JOIN when I want to grab all the fields of one table but only selected fields from the other table(s)?
For instance, in mysql we can simply do:
SELECT tb1.*, tb2.b, tb2.d
FROM tableA tb1
INNER JOIN tableB tb2 ON tb1.x = tb2.a
However, OpenSQL does not seem to allow selecting tb1~*, tb2~b, tb2~d so I have to resort to this:
SELECT tb1.x, tb1.y, tb1.z, tb2.b, tb2.d
FROM tableA tb1
INNER JOIN tableB tb2 ON tb1.x = tb2.a
For very large tables, especially standard tables, this becomes unwieldy, difficult to read and more annoying to maintain.
Is there a better way to select all fields of tb1 and some fields from tb2?
Yes, this is possible in the OpenSQL from 7.40 SP08. See this article.
The quotation from the article has that.
Column Specification
In the SELECT list, you can specify all columns of a data source using the syntax data_source~* from 7.40, SP08 on. This can be handy when working with joins.
SELECT scarr~carrname, spfli~*, scarr~url
FROM scarr INNER JOIN spfli ON scarr~carrid = spfli~carrid
INTO TABLE #DATA(result).
In the previous versions unfortunately one has to specify the columns one by one or use database native SQL for example with ADBC.
Related
I am working with a dataset of tables that (a) often requires joining tables together, however also (b) frequently has duplicate columns names. Any time I write a query along the lines of:
SELECT
t1.*, t2.*
FROM t1
LEFT JOIN t2 ON t1.this_id = t2.matching_id
...I get the error Duplicate column names in the result are not supported. Found duplicate(s): this_col, that_col, another_col, more_cols, dupe_col, get_the_idea_col
I understand that with BigQuery, it is better to avoid using * when selecting tables, however my data tables aren't too big + my bigquery budget is high, and doing these joins with all columns helps significantly with data exploration.
Is there anyway BigQuery can automatically handle / rename columns in these situations (e.g. prefix the column with the table name), as opposed to not allowing the query all together?
Thanks!
The simplest way is to select records rather than columns:
SELECT t1, t2
FROM t1 LEFT JOIN
t2
ON t1.this_id = t2.matching_id;
This is pretty much what I do for ad hoc queries.
If you want the results as columns and not records (they don't look much different in the results), you can use EXCEPT:
SELECT t1.* EXCEPT (duplicate_column_name),
t2.* EXCEPT (duplicate_column_name),
t1.duplicate_column_name as t1_duplicate_column_name,
t2.duplicate_column_name as t2_duplicate_column_name
FROM t1 LEFT JOIN
t2
ON t1.this_id = t2.matching_id;
Is there anyway BigQuery can automatically handle / rename columns in these situations (e.g. prefix the column with the table name), as opposed to not allowing the query all together?
This is possible with BigQuery Legacy SQL - which can be handy for data exploration unless you are dealing with data types or using some functions/features specific to standard sql
So below
#legacySQL
SELECT t1.*, t2.*
FROM table1 AS t1
LEFT JOIN table2 AS t2
ON t1.this_id = t2.matching_id
will produce output where all column names will be prefixed with respective alias like t1_this_id and t2_matching_id
I have many tables that are all named similarly (like "table1" "table2" "table3" etc.) and I need to use all of them in a query. They all contain the same two variables ("ID" and "date") that they are joined on.
There are at least 25 tables of this sort and I have read-only access to the database so I can't combine them or even create a view that would do so.
My question is: Is there a simple shortcut I can use to join all these tables? If this were SAS I would create a macro, but I'm using Microsoft SQL Server Management Studio 2012.
Instead of having to do this:
select *
from table1 a
join table2 b on a.id=b.id and a.date=b.date
join table3 c on b.id=c.id and b.date=c.date
join ....
join ....
join table25 y on x.id=y.id and x.date=y.date
I'd like to do something like:
select *
from merge(table1 - table25) using(id, date)
Replacing the "merge" statement above with whatever is appropriate. Is such a thing possible?
As pointed out in the comments, the succinct syntax you are looking for doesn't exist.
The only way to shorten the SQL that takes advantage of the fact that the joining columns are all named the same would involve using the using keyword:
select *
from table1 a
join table2 b using (id, date)
join table3 c using (id, date)
join ....
join ....
join table25 y using (id, date)
But sadly, even that won't work for you, because the using keyword is not recognized in SQL Server. It does work in other popular databases though.
I know that joins work by combining two or more tables by their attributes, so if you have two tables that both have three columns and both have column INDEX, if you use table1 JOIN table2 you will get a new table with 5 columns, but what if you do not have a column that is shared by both table1 and table2? Can you still use JOIN or do you have to use TIMES?
Join is not a method for combining tables. It is a method to select records (and selected fields) from 2 or more tables where every table in the query must carry a field that can be matched to a field in another table in the query. The matched fields need not have the same name, but must carry the same type of data. Lacking this would be like trying to create meaning from joining a list of license plates of cars in NYC, with height data from lumberjacks in Washington state -- not meaningful.
Ex:)
Select h.name, h.home_address, h.home_phone, w.work_address,
w.department
from home h, work w
where h.employee_id = w.emp_id
As long as both columns: employee_id and emp_id carry the same information this query will work
In Microsoft Access, to get five rows from a three column table joined to a two column table, you'd use:
SELECT Table1.*, Table2.* FROM Table1 INNER JOIN Table2 ON Table1.Field1 = Table2.Field1;
You can query whatever you want, and join whatever you want, though.
If your one table is a list of people, and your other is a list of cars, and you want to see what people have names that are also models of cars, you can do:
SELECT Table1.Name, Table1.Age, Table2.Make, Table2.Year
FROM Table1 INNER JOIN Table2 ON Table1.Name = Table2.Model;
Only when Name is the same as Model will it show a record.
This is the same idea for joining tables in any relational DBMS I've used.
You are right you can join two tables even if they do not have shared column.
Join uses primary to prevent mistakes on inserting or deleting when user trying to insert record that does not has a parent one or some thing like this.
join methods has many types you can view them here:
http://dev.mysql.com/doc/refman/5.7/en/join.html
LEFT JOIN: select all records from first table, then selecting all records from second table that fulfilling the condition after ON clause.
you can't join the tables if they do not share a common column. If you can find a 3rd table that has common columns with table1 and table2 you can get them to join that way. so join table2 and tabl3 on a common column and than join table3 back to table1 on a common column.
I have two tables, Table A and Table B. Each table have 4 fields, the name of the fields are the same for both. Both tables are extracted from other tables, and each record acts as a primary key.
I want to write a query in MS Access 2010 that gets the data unique to Table B and not shared with Table A. I am using the following image as a reference, and it looks like I need to do a Right Join.
Hello. There is something not right with my SQL, I've tested it and I am getting the incorrect result. Below is the closest I've gotten:
SELECT DISTINCT TableB.*
FROM TableB RIGHT JOIN TableA ON (TableB.Field1 = TableA.Field1) AND (TableB.Field2 = TableA.Field2) AND (TableB.Field3 = TableA.Field3) AND (TableB.Field4 = TableA.Field4)
WHERE (((TableA.Field1) Is Null));
I think it would be clearer for you to use not exists:
select tableb.*
from tableb
where not exists (select 1
from tablea
where (TableB.Field1 = TableA.Field1) AND (TableB.Field2 = TableA.Field2) AND (TableB.Field3 = TableA.Field3) AND (TableB.Field4 = TableA.Field4)
);
Your use of RIGHT JOIN is incorrect. As phrased, you want a LEFT JOIN. That is, you want to keep all rows in the first table (the "left" table in the JOIN) regardless of whether or not a match exists in the second table. However, the NOT EXISTS does the same thing and the logic is a bit clearer.
You want to have right join if tablea is in your select statement, but as you have
SELECT DISTINCT TableB.*
you may want to have a left join instead. My suggestion would be changing your code from right to left join.
TableB acts like table A from venn diagrams above.
I'm trying to get data from a table which is only related through two different tables. For example, I have information "dataA" and need to get information "dataD".
How do I write a query to display dataA and dataD as they relate? I don't want to display all instances of dataD, just the ones that related to dataB and then to dataA. I'm sorry if this doesn't make enough sense.
You'll use JOINs to do this. Specifically, in this case, a LEFT OUTER JOIN is your best bet. Something like:
SELECT
Table1.dataA,
Table3.dataD
FROM
Table1
LEFT OUTER JOIN Table2 ON Table1.dataB = Table2.dataB
LEFT OUTER JOIN Table3 ON Table2.dataC = Table3.dataC
Working on the assumption that the "data" entries you put under each table name represent columns in the table, this is fairly simple:
select dataA
, dataD
from Table1 t1
join Table2 t2
on t1.dataB = t2.dataB
join Table3 t3
on T2.dataC = t3.dataC
If you need all the dataA regardless of whether there's a matching dataD (or other intervening column) you would change where I wrote 'join' to 'left join'.
And your question makes plenty of sense. :) I was just a little unclear from the diagram what you had in mind.