When writing a self-join in tSQL I can avoid duplicate column names thus:
SELECT FirstEvent.Title AS FirstTitle, SecondEvent.Title AS FirstTitle
FROM ContiguatedEvents AS FirstEvent
LEFT OUTER JOIN ContiguatedEvents AS SecondEvent
ON FirstEvent.logID = SecondEvent.logID
Suppose I want to select all the columns from the self-join, for example into a view. How do I then differentiate the column names without writing each one out in the join statement. I.e. is there anything I can write like this (ish)
SELECT FirstEvent.* AS ???, SecondEvent.* AS ???
FROM ContiguatedEvents AS FirstEvent
LEFT OUTER JOIN ContiguatedEvents AS SecondEvent
ON FirstEvent.logID = SecondEvent.logID
There's no way to automatically introduce aliases for multiple columns, you just have to do it by hand.
One handy hint for quickly getting all of the column names into your query (in management studio) is to drag the Columns folder from the Object Explorer into a query window. It gives you all of the column names.
Related
I have been trying to do an outer join across two different tables in two different schemas. I am trying to filter out before from the table variants the character that are smaller than 4 and bigger than 5 digits. The join was not working with a simply where clause in the end, hence this decision.
The problem is if I do not put the quotes, Snowflake will say that I put invalid identifiers. However, when I run this with the quotes, it works but I get as values in the fields of the column raw.stitch_heroku.spree_variants.SKU only named as the column name, all across the table!
SELECT
analytics.dbt_lcasucci.product_category.product_description,
'raw.stitch_heroku.spree_variants.SKU'
FROM analytics.dbt_lcasucci.product_category
LEFT JOIN (
SELECT * FROM raw.stitch_heroku.spree_variants
WHERE LENGTH('raw.stitch_heroku.spree_variants.SKU')<=5
and LENGTH('raw.stitch_heroku.spree_variants.SKU')>=4
) ON 'analytics.dbt_lcasucci.product_category.product_id'
= 'raw.stitch_heroku.spree_variants.SKU'
Is there a way to work this around? I am confused and have not found this issue on forums yet!
thx in advance
firstly single quote define a string literal 'this is text' where as double quotes are table/column names "this_is_a_table_name"
add alias's to the tables makes the SQL more readable, and the duplicate length command can be reduced with a between, thus this should work better:
SELECT pc.product_description,
sp.SKU
FROM analytics.dbt_lcasucci.product_category AS PC
LEFT JOIN (
SELECT SKU
FROM raw.stitch_heroku.spree_variants
WHERE LENGTH(SKU) BETWEEN 4 AND 5
) AS sp
ON pc.product_id = sp.SKU;
So I reduced the sub-selects results as you only used sku from sp but given you are comparing product_id to sku as your example exists you don't need to join to sp.
the invalid indentifiers implies to me something is named incorrectly, the first step there is to check the tables exist and the columns are named as you expect and the type of the columns are the same for the JOIN x ON y clause via:
describe table analytics.dbt_lcasucci.product_category;
describe table raw.stitch_heroku.spree_variants;
Hi I am trying to Left outer join on table onto another, the matching colums are type String.
Will Hive join on matching string columns or do they need to be converted to a different datatype?
My join ON Clause looks like
Select table1.para1, table2.para2
From table a
left outer Join Table b
On (table1.a=table2.b). A and B are strings, will this work?
Join on string will work. Just keep in mind that string matching will be case-sensitive.
Consider using functions like UPPER or LOWER.
For example,
select * from temp join new_temp on LOWER(temp.dept) = LOWER(new_temp.dept);
Perhaps I'm approaching this all wrong, in which case feel free to point out a better way to solve the overall question, which "How do I use an intermediate table for future queries?"
Let's say I've got tables foo and bar, which join on some baz_id, and I want to use combine this into an intermediate table to be fed into upcoming queries. I know of the WITH .. AS (...) statement, but am running into problems as such:
WITH foobar AS (
SELECT *
FROM foo
INNER JOIN bar ON bar.baz_id = foo.baz_id
)
SELECT
baz_id
-- some other things as well
FROM
foobar
The issue is that (Postgres 9.4) tells me baz_id is ambiguous. I understand this happens because SELECT * includes all the columns in both tables, so baz_id shows up twice; but I'm not sure how to get around it. I was hoping to avoid copying the column names out individually, like
SELECT
foo.var1, foo.var2, foo.var3, ...
bar.other1, bar.other2, bar.other3, ...
FROM foo INNER JOIN bar ...
because there are hundreds of columns in these tables.
Is there some way around this I'm missing, or some altogether different way to approach the question at hand?
WITH foobar AS (
SELECT *
FROM foo
INNER JOIN bar USING(baz_id)
)
SELECT
baz_id
-- some other things as well
FROM
foobar
It leaves only one instance of the baz_id column in the select list.
From the documentation:
The USING clause is a shorthand that allows you to take advantage of the specific situation where both sides of the join use the same name for the joining column(s). It takes a comma-separated list of the shared column names and forms a join condition that includes an equality comparison for each one. For example, joining T1 and T2 with USING (a, b) produces the join condition ON T1.a = T2.a AND T1.b = T2.b.
Furthermore, the output of JOIN USING suppresses redundant columns: there is no need to print both of the matched columns, since they must have equal values. While JOIN ON produces all columns from T1 followed by all columns from T2, JOIN USING produces one output column for each of the listed column pairs (in the listed order), followed by any remaining columns from T1, followed by any remaining columns from T2.
I have a report where I need to join two tables but the fields are defined differently between them and I cannot change the table schemas because its JDEdwards. So I have one field as 30 characters left aligned and another another as 12 characters right aligned. The values will always be under 12 characters. So the issue is not the difference in size but the alignment/padding. I have to do a left join though. Right now the report is just comparing in the data selection and causing an inner join. But I need to change it to left join to stop losing rows. Is there any way to do it?
What happens is when I create the link to do the left join in Database Expert, I end up getting the data from the joined table all blank due to it not finding any rows because of the padding difference.
Since you only need one value from the table to be joined you can instead create a single SQL Expression to get the value for you without the need to add any tables to the report itself via Database Expert. You'll be able to use any valid SQL so you can do pretty much whatever you want without being constrained by Crystal.
For example, say your report consists of Table_A with a foreign key that is 30-characters left-aligned and you're trying to join to Table_B to get at some field, but that key is 12 characters right-aligned. A simple example in Oracle would be something like this:
case when "Table_A"."ForeignKey" is null then null
else
(select Table_B.SomeFieldYouWant
from Table_B
where rpad(Table_B.PrimaryKey,30,'0')="Table_A"."ForeignKey"
end
It's important to note that in a SQL Expression, any fields referenced with double quotes means that it's referring back to tables/fields in your report instead of new tables in the subquery; this is how you relate the subquery back to your report's data.
I am developing a t-sql query to return left join of two tables, but when I just select records from Table A, it gives me only 2 records. The problem though is when I left join it Table B, it gives me 4 records. How can I reduce this to just 2 records?
One problem though is that I am only aware of one PK/FK to link these two tables.
The field you are using for the join must exist more than once in table B - this is why multiple rows are being returned in the join. In order to reduce the row count you will have to either add further fields to the join, or add a where clause to filter out rows not required.
Alternatively you could use a GROUP BY statement to group the rows up, but this may not be what you need.
Remember that the left join brings you null fields from joined table.
Also you can use select(distinct), but i can't see well you issue. Can you give us more details?