非常复杂的(Postgre / My)SQL示例吗？

在测试abstraction concepts或在使用Postgresql,MysqL甚至sqlite时比较数据库样式和结构时,我经常发现自己需要非常复杂的sql示例.

我认为这意味着还有其他一些人需要疯狂的查询来打开我们的视线,并确保我们的数据库层能够处理我们扔给他们的所有内容.

因此,任何人都可以共享一些查询,即使是最顽固的ORM专家也可以通过这些查询进行循环吗？

SELECT [ ALL | disTINCT [ ON ( expression [, ...] ) ] ]
    * | expression [ [ AS ] output_name ] [, ...]
    [ FROM from_item [, ...] ]
    [ WHERE condition ]
    [ GROUP BY expression [, ...] ]
    [ HAVING condition [, ...] ]
    [ WINDOW window_name AS ( window_deFinition ) [, ...] ]
    [ { UNION | INTERSECT | EXCEPT } [ ALL ] select ]
    [ ORDER BY expression [ ASC | DESC | USING operator ] [ NULLS { FirsT | LAST } ] [, ...] ]
    [ LIMIT { count | ALL } ]
    [ OFFSET start [ ROW | ROWS ] ]
    [ FETCH { FirsT | NEXT } [ count ] { ROW | ROWS } ONLY ]
    [ FOR { UPDATE | SHARE } [ OF table_name [, ...] ] [ NowAIT ] [...] ]

MySQL

SELECT
    [ALL | disTINCT | disTINCTROW ]
      [HIGH_PRIORITY]
      [STRAIGHT_JOIN]
      [sql_SMALL_RESULT] [sql_BIG_RESULT] [sql_BUFFER_RESULT]
      [sql_CACHE | sql_NO_CACHE] [sql_CALC_FOUND_ROWS]
    select_expr [, select_expr ...]
    [FROM table_references
    [WHERE where_condition]
    [GROUP BY {col_name | expr | position}
      [ASC | DESC], ... [WITH ROLLUP]]
    [HAVING where_condition]
    [ORDER BY {col_name | expr | position}
      [ASC | DESC], ...]
    [LIMIT {[offset,] row_count | row_count OFFSET offset}]
    [PROCEDURE procedure_name(argument_list)]
    [INTO OUTFILE 'file_name'
        [CHaraCTER SET charset_name]
        export_options
      | INTO DUMPFILE 'file_name'
      | INTO var_name [, var_name]]
    [FOR UPDATE | LOCK IN SHARE MODE]]

解决方法:

在2009年11月的OpensqlCamp上查看此演讲.

标题：SQL For the Insane

也
Recursion with SQL

问题

假设您正在跟踪耗材,并且有一个名为si_item的字段,另一个名为si_parentid.父级跟踪供应物料所属的子类.例如.您的纸质父级具有子类,例如回收的,未回收的.当有人拿到补给品时,您想返回全限定名,例如纸张->回收-> 20 Lb

解

CREATE TABLE supplyitem(si_id integer PRIMARY KEY, si_parentid integer, si_item varchar(100));

--load up the table (multirow constructor introduced in 8.2)
INSERT INTO supplyitem(si_id,si_parentid, si_item)
VALUES (1, NULL, 'Paper'),
(2,1, 'Recycled'),
(3,2, '20 lb'),
(4,2, '40 lb'),
(5,1, 'Non-Recycled'),
(6,5, '20 lb'),
(7,5, '40 lb'),
(8,5, 'Scraps');

--Recursive query (introduced in 8.4 returns fully qualified name)
WITH RECURSIVE supplytree AS
(SELECT si_id, si_item, si_parentid, CAST(si_item As varchar(1000)) As si_item_fullname
FROM supplyitem
WHERE si_parentid IS NULL
UNION ALL
SELECT si.si_id,si.si_item,
    si.si_parentid,
    CAST(sp.si_item_fullname || '->' || si.si_item As varchar(1000)) As si_item_fullname
FROM supplyitem As si
    INNER JOIN supplytree AS sp
    ON (si.si_parentid = sp.si_id)
)
SELECT si_id, si_item_fullname
FROM supplytree
ORDER BY si_item_fullname;

结果看起来像

si_id |      si_item_fullname
------+-----------------------------
 1    | Paper
 5    | Paper->Non-Recycled
 6    | Paper->Non-Recycled->20 lb
 7    | Paper->Non-Recycled->40 lb
 8    | Paper->Non-Recycled->Scraps
 2    | Paper->Recycled
 3    | Paper->Recycled->20 lb
 4    | Paper->Recycled->40 lb

非常复杂的(Postgre / My)SQL示例吗？

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