CODEWITHSUNDEEP
sql
turnip
turnip

Reputation: 2346

WITH clause with a strange alias

I am familiar with what the WITH clause does but I have come across this statement and I am not sure what to make of it:

 WITH
  H AS (SELECT  PS$,HIERY_TYPE,ID$,HIERY_PS$_PARENT,HIERY_TYPE_PARENT,HIERY_ID$_PARENT,LABEL  FROM RSPC_HIERARCHY WHERE PS$='SDH' AND HIERY_TYPE LIKE 'STARS%'),
  H_TREE(XLEVEL, STARS_FAMILY,PS$,HIERY_TYPE,ID$,HIERY_PS$_PARENT,HIERY_TYPE_PARENT,HIERY_ID$_PARENT,LABEL) AS
      (
      SELECT 1 XLEVEL,  ID$ STARS_FAMILY ,  PS$,HIERY_TYPE,ID$,HIERY_PS$_PARENT,HIERY_TYPE_PARENT,HIERY_ID$_PARENT,LABEL  FROM H WHERE  HIERY_TYPE ='STARS_FAMILY'
      UNION ALL
      SELECT  HT.XLEVEL + 1 XLEVEL, HT.STARS_FAMILY,H.PS$,H.HIERY_TYPE,H.ID$,H.HIERY_PS$_PARENT,H.HIERY_TYPE_PARENT,H.HIERY_ID$_PARENT, H.LABEL
      FROM H, H_TREE HT)

In particular, I don't understand the H_TREE alias. What is the function of the stuff in the parenthesis?

Upvotes: 1

Views: 28

Answers (1)

Gordon Linoff
Gordon Linoff

Reputation: 1270443

The "stuff in parentheses" simply a list of the names of the columns for the alias. I think create view supports the same construct.

Normally, the column names are taken directly from the select. But they can also be specified before the as.

Upvotes: 1

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