Group by Alias (Oracle)

Group by alias (Oracle)

select
  count(count_col),
  alias_column
from
  (
  select 
    count_col, 
    (select value from....) as alias_column 
  from 
    table
  ) as inline
group by 
  alias_column

Grouping normally works if you repeat the respective expression in the GROUP BY clause. Just mentioning an alias is not possible, because the SELECT step is the last step to happen the execution of a query, grouping happens earlier, when alias names are not yet defined.

To GROUP BY the result of a sub-query, you will have to take a little detour and use an nested query, as indicated above.

Alias in Group By clause - invalid identifier

In Oracle and SQL Server, you cannot use a term in the GROUP BY
clause that you define in the SELECT clause because the GROUP BY is
executed before the SELECT clause.

https://stackoverflow.com/a/3841804/6358346

The correct way:

SELECT TRUNC(months_between(sysdate, DateofBirth) / 12) AS "age"
FROM players
GROUP BY TRUNC(months_between(sysdate, DateofBirth) / 12)
HAVING COUNT(TRUNC(months_between(sysdate, DateofBirth) / 12)) > 30;

SQL - using alias in Group By

SQL is implemented as if a query was executed in the following order:

1. FROM clause
2. WHERE clause
3. GROUP BY clause
4. HAVING clause
5. SELECT clause
6. ORDER BY clause

For most relational database systems, this order explains which names (columns or aliases) are valid because they must have been introduced in a previous step.

So in Oracle and SQL Server, you cannot use a term in the GROUP BY clause that you define in the SELECT clause because the GROUP BY is executed before the SELECT clause.

There are exceptions though: MySQL and Postgres seem to have additional smartness that allows it.

Why doesn't Oracle SQL allow us to use column aliases in GROUP BY clauses?

It isn't just Oracle SQL, in fact I believe it is conforming to the ANSI SQL standard (though I don't have a reference for that). The reason is that the SELECT clause is logically processed after the GROUP BY clause, so at the time the GROUP BY is done the aliases don't yet exist.

Perhaps this somewhat ridiculous example helps clarify the issue and the ambiguity that SQL is avoiding:

SQL> select job as sal, sum(sal) as job
  2  from scott.emp
  3  group by job;

SAL              JOB
--------- ----------
ANALYST         6000
CLERK           4150
MANAGER         8275
PRESIDENT       5000
SALESMAN        5600

Can't use column alias in GROUP BY

As mentioned in another answer, You can not add aliases in GROUP BY but you can add aliases in ORDER BY. Also, DATE_FORMAT is MySql function. It is TO_CHAR in Oracle.

So your final query should be as following:

SELECT
    TO_CHAR(TRANS_DATE, 'YYYY-MM') AS MONTH,
    COUNTRY,
    COUNT(*) AS TRANS_COUNT,
    SUM(CASE WHEN STATE = 'approved'  THEN 1 ELSE 0 END) AS APPROVED_COUNT,
    SUM(AMOUNT) AS TRANS_TOTAL_AMOUNT,
    SUM(CASE WHEN STATE = 'approved' THEN AMOUNT ELSE 0 END) AS APPROVED_TOTAL_AMOUNT
FROM TRANSACTIONS
GROUP BY TO_CHAR(TRANS_DATE, 'YYYY-MM'), COUNTRY
ORDER BY MONTH;

group by alias in Oracle

The UNION should remove any duplicates. If it doesn't then you should check the data -- maybe you have extra spaces in the text columns.

Try something like this.

select state1 as state,TRIM(desc1) as desc from table where id=X
Union
select state2 as state,TRIM(desc2) as desc from table where id=X

jOOQ - group by uses alias instead of columns

Note, for this answer, and for brevity reasons, I'm assuming you had been using the code generator. The answer is the same without code generation usage.

Why the current behaviour?

Note, this behaviour is also documented here in the manual.

In jOOQ, an aliased column expression T1.T1_ID.as("id") can only generate 2 different versions of itself:

• T1.T1_ID as ID, i.e. the alias declaration (when inside of SELECT, at the top level)
• ID, i.e. the alias reference (when inside of any other clause / expression than the SELECT clause)

There isn't a third type of generated SQL that depends on the location of where you embed the alias expression, e.g. the unaliased column expression T1.T1_ID when you put the expression in WHERE or GROUP BY, etc. The rationale is simple. What would a user expect when they write:

groupBy(T1.T1_ID.as("id"))

Why would they expect the as() call to be a no-op? That would be more surprising than the status quo.

Consistency with other rendering modes

There are other types of QueryPart in jOOQ, which have similar aliasing capabilities:

• Field
• Table
• WindowSpecification
• Parameter
• CTE

Let's look at the CTE example:

Table<?> cte = name("cte").as(select(...))

That cte reference has 2 modes of rendering itself to SQL:

• The CTE declaration (if placed in the WITH clause)
• The CTE reference (if placed in FROM, etc.)

I don't think you'd expect that cte reference to ever ignore the aliasing, and just render the SELECT itself?

Likewise with table aliasing:

T1 x = T1.as("x");

This can render itself as:

• The alias declaration (if placed in the FROM clause)
• The alias reference

Because the FROM clause is logically before any other clauses, you'd never expect your x reference to render only T1, instead of x or T1 as x, right?

So, for consistency reasons across the jOOQ API, the Field aliases must also behave like all the others.

What to do instead?

Don't re-use the alias expression outside of your SELECT clause. Write the jOOQ SQL exactly as you'd write the actual SQL:

ctx.select(T1.T1_ID.as("id"), ...)
   .from(T1)
   .groupBy(T1.T1_ID)
   ...

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