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Self Nested SQL join


By : user2175754
Date : October 14 2020, 08:10 PM
I hope this helps . I need this result this table. This is 3 column and I want 3 results with nested node. Really I want each node with self and parent like result , This worked for me
code :
;WITH
    cte1 AS
    (   -- Recursively build the relationship tree
        SELECT      SelfRef
                ,   ID
                ,   AscendentLevel = 1
        FROM        [Kharid].[IdentityGharardadKalaTedad]
        UNION ALL
        SELECT      t.SelfRef
                ,   cte1.ID
                ,   AscendentLevel = cte1.AscendentLevel + 1
        FROM        cte1
        INNER JOIN  [Kharid].[IdentityGharardadKalaTedad]    t   ON t.ID = cte1.SelfRef
    ),
    cte2 AS
    (   -- Now find the ultimate parent
        SELECT      SelfRef
                ,   ID
                ,   rn = ROW_NUMBER() OVER (PARTITION BY ID ORDER BY AscendentLevel DESC)
        FROM        cte1
    )

SELECT  *
FROM    cte2
Order by id


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How do I convert this Informix nested join to a tsql nested join?


By : Annika G.
Date : March 29 2020, 07:55 AM
wish of those help Someone's naming conventions leave much to be desired. Also, a SELECT statement starts with SELECT; it feels funny looking at decapitated SQL. It looks like you've got the general idea right.
code :
SELECT *
  FROM      ttdpur401105 AS tdpur401
  JOIN      ttdpur400105 AS tdpur400 ON  tdpur401.t_orno = tdpur400.t_orno 
  LEFT JOIN tarpur002105 AS arpur002 ON  arpur002.t_orno = tdpur401.t_orno 
                                     AND arpur002.t_pono = tdpur401.t_pono 
  LEFT JOIN ttcibd001105 AS tcibd001 ON  tcibd001.t_item = tdpur401.t_item 
  LEFT JOIN (SELECT *
               FROM ttdpur402105 AS tdpur402
               LEFT JOIN (SELECT *
                            FROM      ttisfc001105 AS tisfc001
                            LEFT JOIN ttcibd001105 AS tcibd001a
                              ON tcibd001a.t_item = tisfc001.t_mitm
                         )
                 ON tisfc001.t_pdno = tdpur402.t_pdno
            )
    ON tdpur402.t_orno = tdpur401.t_orno 
   AND tdpur402.t_pono = tdpur402.t_pono   -- ??typo tdpur402.t_pono = tdpur401.t_pono
 WHERE   tdpur401.t_otbp = ' WD005' 
   AND ((tdpur401.t_oltp = 1 AND tdpur401.t_qibo <> 0) OR 
        (tdpur401.t_oltp = 4 AND tdpur401.t_qibo = 0 AND
         tdpur401.t_qidl <> tdpur401.t_qoor)) 
   AND   tdpur401.t_fire <> 1
   AND  (tdpur401.t_orno[1,3]='111' OR tdpur401.t_orno[1,4]='1126' )
   AND  (tdpur400.t_hdst <> 25 AND tdpur400.t_hdst <> 30 AND tdpur400.t_hdst <> 40) 

Nested INNER JOIN vs INNER JOIN vs WHERE: correctness, performance, clarity for a particular case (not a typical JOIN vs


By : Fiskani Lawrence Chi
Date : March 29 2020, 07:55 AM
Hope this helps All database engines I've been closely working with (this is SQL Server, Oracle, PostgreSQL, MySQL, Sybase, SQLite, Informix and Firebird) will optimize it to the same plan.
The fourth query, however, won't parse on all engines (you cannot reference a table in an ON clause before it had been used in a JOIN clause)

Postgres consistently favoring nested loop join over merge join


By : user36176
Date : March 29 2020, 07:55 AM
should help you out The reason is that Postgres is actually doing the right thing, and I suck at math. Suppose table A has N rows, and table B has M rows, and they are being joined via a column that they both have a B-tree index for. Then the following is true:
Nested loop join's time complexity is not O(MN), like I naively thought, but O(M log N) or O(N log M), depending on which table is scanned linearly. If both are scanned by an index, we get O(M log M log N) or O(N log M log N), respectively. But since this is only required if a specific order of the rows is needed for yet another join or due to the ORDER clause, as we'll see it's not a bad deal at all. Merge join's time complexity is O(M log M + N log N), which means that it loses to the nested loop join, provided that the asymptotic proportionality coefficients are the same, and AFAIK they should both be equal to 1 in most implementations. Since both tables must be iterated by the same index in the same direction, if different order is required, an additional sort is required, which easily makes the complexity worse than in the case of the nested loop sort.

why Indexed Nested-Loop Join only applicable for equi-join or natural join?


By : JAC
Date : March 29 2020, 07:55 AM
will help you You are quoting slides for Database Systems Concepts (c) Silberschatz, Korth and Sudarshan.
We want the DBMS to calculate a join. There are lots of special cases where it can do it various ways. These might involve whether there are indexes, selection conditions, etc.

SQL array flattening: Why doesn't CROSS JOIN UNNEST join every nested value with every row?


By : Tim Wright
Date : March 29 2020, 07:55 AM
I wish this help you The best way to think about this is by looking at what happens on a row-by-row basis. Setting up some input data, we have:
code :
WITH t1 AS (
  SELECT 1 AS id, [0, 1] AS numbers_array UNION ALL
  SELECT 2, [2, 4, 5]
)
...
WITH t1 AS (
  SELECT 1 AS id, [0, 1] AS numbers_array UNION ALL
  SELECT 2, [2, 4, 5]
)
SELECT * FROM t1;
+----+---------------+
| id | numbers_array |
+----+---------------+
| 1  | [0, 1]        |
| 2  | [2, 4, 5]     |
+----+---------------+
+-----+
| f0_ |
+-----+
| 0   |
| 1   |
+-----+
SELECT * FROM UNNEST([0, 1]);
+-----+
| f0_ |
+-----+
| 2   |
| 4   |
| 5   |
+-----+
WITH t1 AS (
  SELECT 1 AS id, [0, 1] AS numbers_array UNION ALL
  SELECT 2, [2, 4, 5]
)
SELECT id, number
FROM t1
CROSS JOIN UNNEST(numbers_array) AS number;
+----+--------+
| id | number |
+----+--------+
| 1  | 0      |
| 1  | 1      |
| 2  | 2      |
| 2  | 4      |
| 2  | 5      |
+----+--------+
WITH t1 AS (
  SELECT 1 AS id, [0, 1] AS numbers_array UNION ALL
  SELECT 2, [2, 4, 5]
), t2 AS (
  SELECT number
  FROM t1
  CROSS JOIN UNNEST(numbers_array) AS number
)
SELECT number
FROM t2;
+--------+
| number |
+--------+
| 0      |
| 1      |
| 2      |
| 4      |
| 5      |
+--------+
WITH t1 AS (
  SELECT 1 AS id, [0, 1] AS numbers_array UNION ALL
  SELECT 2, [2, 4, 5]
), t2 AS (
  SELECT number
  FROM t1
  CROSS JOIN UNNEST(numbers_array) AS number
)
SELECT id, numbers_array, number
FROM t1
CROSS JOIN t2;
+----+---------------+--------+
| id | numbers_array | number |
+----+---------------+--------+
| 1  | [0, 1]        | 0      |
| 1  | [0, 1]        | 1      |
| 1  | [0, 1]        | 2      |
| 1  | [0, 1]        | 4      |
| 1  | [0, 1]        | 5      |
| 2  | [2, 4, 5]     | 0      |
| 2  | [2, 4, 5]     | 1      |
| 2  | [2, 4, 5]     | 2      |
| 2  | [2, 4, 5]     | 4      |
| 2  | [2, 4, 5]     | 5      |
+----+---------------+--------+
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