实现 SQL 嵌套游标的最佳方法是什么

Question

有人可以告诉我使用提供的数据集实现嵌套游标的最佳方法吗？

正如您将看到的，已经有一个 Cursor 查找 #TMP_CODE1 中列出的值，如果匹配则执行 select 语句并将结果插入到输出 table.

我正在尝试使用嵌套游标对存储在#TMP_CODE2.

中的值复制相同的过程

我想打印@Numbers 的方式与将@Letters 插入到下面的#Output table 中的方式相同：

  PRINT @Letters;
  INSERT INTO #Output ([Dummy Column1], [Dummy Column2]) VALUES ('Letters:', @Letters)
  INSERT INTO #Output ([Dummy Column1]) VALUES ('')

每行组合在一起，代码显示在每个结果集上方。

只有在#TMP_CODE1 和#TMP_CODE2 临时 table 中列出的值才能插入输出 table。

DROP TABLE IF EXISTS #TMP_CODE1
CREATE TABLE #TMP_CODE1(Letters varchar(3));
INSERT INTO #TMP_CODE1(Letters) VALUES 
  ('AAA'),('BBB'),('CCC'),('DDD'),('EEE'),('FFF');

DROP TABLE IF EXISTS #TMP_CODE2
CREATE TABLE #TMP_CODE2(Numbers varchar(3));
INSERT INTO #TMP_CODE2(Numbers) VALUES 
  ('111'),('222'),('333'),('444'),('555'),('666');

DROP TABLE IF EXISTS #Input
CREATE TABLE #Input (CODE1 varchar(3), [Dummy Column1] varchar (15), 
[Dummy Column2] varchar (15), CODE2 varchar(3), [Dummy Column3] varchar (15),
[Dummy Column4] varchar (15));

DROP TABLE IF EXISTS #Output
CREATE TABLE #Output (CODE1 varchar(3), [Dummy Column1] varchar (15), 
[Dummy Column2] varchar (15), CODE2 varchar(3), [Dummy Column3] varchar (15),
[Dummy Column4] varchar (15));

INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('AAA', 'DUMMY DATA 1 1', 'DUMMY DATA 2 1', '111', 'DUMMY DATA 3 1', 'DUMMY DATA 4 1')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('AAA', 'DUMMY DATA 1 2', 'DUMMY DATA 2 2', '111', 'DUMMY DATA 3 2', 'DUMMY DATA 4 2')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('AAA', 'DUMMY DATA 1 3', 'DUMMY DATA 2 3', '111', 'DUMMY DATA 3 3', 'DUMMY DATA 4 3')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('AAA', 'DUMMY DATA 1 4', 'DUMMY DATA 2 4', '222', 'DUMMY DATA 3 4', 'DUMMY DATA 4 4')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('AAA', 'DUMMY DATA 1 5', 'DUMMY DATA 2 5', '333', 'DUMMY DATA 3 5', 'DUMMY DATA 4 5')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('AAA', 'DUMMY DATA 1 6', 'DUMMY DATA 2 6', '555', 'DUMMY DATA 3 6', 'DUMMY DATA 4 6')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('BBB', 'DUMMY DATA 1 7', 'DUMMY DATA 2 7', '222', 'DUMMY DATA 3 7', 'DUMMY DATA 4 7')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('BBB', 'DUMMY DATA 1 8', 'DUMMY DATA 2 8', '111', 'DUMMY DATA 3 8', 'DUMMY DATA 4 8')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('BBB', 'DUMMY DATA 1 9', 'DUMMY DATA 2 9', '555', 'DUMMY DATA 3 9', 'DUMMY DATA 4 9')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('BBB', 'DUMMY DATA 1 10', 'DUMMY DATA 2 10', '444', 'DUMMY DATA 3 10', 'DUMMY DATA 4 10')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('BBB', 'DUMMY DATA 1 11', 'DUMMY DATA 2 11', '777', 'DUMMY DATA 3 11', 'DUMMY DATA 4 11')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('BBB', 'DUMMY DATA 1 12', 'DUMMY DATA 2 12', '888', 'DUMMY DATA 3 12', 'DUMMY DATA 4 12')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('BBB', 'DUMMY DATA 1 13', 'DUMMY DATA 2 13', '222', 'DUMMY DATA 3 13', 'DUMMY DATA 4 13')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('BBB', 'DUMMY DATA 1 14', 'DUMMY DATA 2 14', '111', 'DUMMY DATA 3 14', 'DUMMY DATA 4 14')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('BBB', 'DUMMY DATA 1 15', 'DUMMY DATA 2 15', '222', 'DUMMY DATA 3 15', 'DUMMY DATA 4 15')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('BBB', 'DUMMY DATA 1 16', 'DUMMY DATA 2 16', '666', 'DUMMY DATA 3 16', 'DUMMY DATA 4 16')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('CCC', 'DUMMY DATA 1 17', 'DUMMY DATA 2 17', '111', 'DUMMY DATA 3 17', 'DUMMY DATA 4 17')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('CCC', 'DUMMY DATA 1 18', 'DUMMY DATA 2 18', '111', 'DUMMY DATA 3 18', 'DUMMY DATA 4 18')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('DDD', 'DUMMY DATA 1 19', 'DUMMY DATA 2 19', '111', 'DUMMY DATA 3 19', 'DUMMY DATA 4 19')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('DDD', 'DUMMY DATA 1 20', 'DUMMY DATA 2 20', '222', 'DUMMY DATA 3 20', 'DUMMY DATA 4 20')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('DDD', 'DUMMY DATA 1 21', 'DUMMY DATA 2 21', '333', 'DUMMY DATA 3 21', 'DUMMY DATA 4 21')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('DDD', 'DUMMY DATA 1 22', 'DUMMY DATA 2 22', '555', 'DUMMY DATA 3 22', 'DUMMY DATA 4 22')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('EEE', 'DUMMY DATA 1 23', 'DUMMY DATA 2 23', '222', 'DUMMY DATA 3 23', 'DUMMY DATA 4 23')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('EEE', 'DUMMY DATA 1 24', 'DUMMY DATA 2 24', '111', 'DUMMY DATA 3 24', 'DUMMY DATA 4 24')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('EEE', 'DUMMY DATA 1 25', 'DUMMY DATA 2 25', '555', 'DUMMY DATA 3 25', 'DUMMY DATA 4 25')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('EEE', 'DUMMY DATA 1 26', 'DUMMY DATA 2 26', '444', 'DUMMY DATA 3 26', 'DUMMY DATA 4 26')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('EEE', 'DUMMY DATA 1 27', 'DUMMY DATA 2 27', '777', 'DUMMY DATA 3 27', 'DUMMY DATA 4 27')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('FFF', 'DUMMY DATA 1 28', 'DUMMY DATA 2 28', '888', 'DUMMY DATA 3 28', 'DUMMY DATA 4 28')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('FFF', 'DUMMY DATA 1 29', 'DUMMY DATA 2 29', '222', 'DUMMY DATA 3 29', 'DUMMY DATA 4 29')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('FFF', 'DUMMY DATA 1 30', 'DUMMY DATA 2 30', '111', 'DUMMY DATA 3 30', 'DUMMY DATA 4 30')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('FFF', 'DUMMY DATA 1 31', 'DUMMY DATA 2 31', '222', 'DUMMY DATA 3 31', 'DUMMY DATA 4 31')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('GGG', 'DUMMY DATA 1 32', 'DUMMY DATA 2 32', '666', 'DUMMY DATA 3 32', 'DUMMY DATA 4 32')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('GGG', 'DUMMY DATA 1 33', 'DUMMY DATA 2 33', '222', 'DUMMY DATA 3 33', 'DUMMY DATA 4 33')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('GGG', 'DUMMY DATA 1 34', 'DUMMY DATA 2 34', '111', 'DUMMY DATA 3 34', 'DUMMY DATA 4 34')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('GGG', 'DUMMY DATA 1 35', 'DUMMY DATA 2 35', '555', 'DUMMY DATA 3 35', 'DUMMY DATA 4 35')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('HHH', 'DUMMY DATA 1 36', 'DUMMY DATA 2 36', '888', 'DUMMY DATA 3 36', 'DUMMY DATA 4 36')
INSERT INTO #Input (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3], [Dummy Column4]) VALUES ('HHH', 'DUMMY DATA 1 37', 'DUMMY DATA 2 37', '555', 'DUMMY DATA 3 37', 'DUMMY DATA 4 37')
  
DECLARE @Letters varchar(3), @c cursor;
    
SET @c = cursor LOCAL FAST_FORWARD
    FOR SELECT Letters FROM #TMP_CODE1;

OPEN @c;
FETCH NEXT FROM @c INTO @Letters;

WHILE @@FETCH_STATUS = 0
BEGIN

  PRINT @Letters;
  INSERT INTO #Output ([Dummy Column1], [Dummy Column2]) VALUES ('Letters:', @Letters)
  INSERT INTO #Output ([Dummy Column1]) VALUES ('')

  INSERT INTO #Output (CODE1, [Dummy Column1], [Dummy Column2], CODE2, [Dummy Column3],[Dummy Column4])
  SELECT * FROM #Input WHERE CODE1 = @Letters

  FETCH NEXT FROM @c INTO @Letters;

END

SELECT * FROM #Output

所以我希望实现的结构是这样的：

这仅适用于 AAA，我希望能够以这种格式格式化示例代码中提供的所有数据。

我正在使用 SQL 服务器，希望能以标准 SQL 的方式回答问题。

谢谢

Answer 1

我先说这个真的应该在表示层完成，而不是在SQL。

尽管如此，您实际上可以按照您想要的顺序获取您想要的所有行，小心使用 GROUPING SETS 和 ORDER BY:

SELECT
  CODE1           = CASE WHEN GROUPING(i.[Dummy Column1]) = 0 THEN CODE1 END,
  [Dummy Column1] = CASE WHEN GROUPING(i.CODE2) = 1 AND GROUPING(i.[Dummy Column1]) = 1
                           THEN 'Letters'
                         WHEN GROUPING(i.[Dummy Column1]) = 1
                           THEN 'Numbers'
                         ELSE i.[Dummy Column1] END,
  [Dummy Column2] = CASE WHEN GROUPING(i.CODE2) = 1 AND GROUPING(i.[Dummy Column1]) = 1
                           THEN i.CODE1
                         WHEN GROUPING(i.[Dummy Column1]) = 1
                           THEN i.CODE2
                         ELSE i.[Dummy Column1] END,
  CODE2           = CASE WHEN GROUPING(i.[Dummy Column1]) = 0 THEN CODE2 END,
  i.[Dummy Column3],
  i.[Dummy Column4]
FROM #Input i
GROUP BY GROUPING SETS (
    (i.CODE1),
    (i.CODE1, i.CODE2),
    (i.CODE1, i.CODE2, i.[Dummy Column1], i.[Dummy Column2], i.[Dummy Column3], i.[Dummy Column4])
)
ORDER BY
  i.CODE1,
  GROUPING(i.CODE2) DESC,
  i.CODE2,
  GROUPING(i.[Dummy Column1]) DESC;

db<>fiddle

GROUPING SETS可以return小计和总计。它比 ROLLUP.

更灵活

GROUPING() 函数告诉您某列是否已在该特定行中分组。您可以在 ORDER BY 中使用它来使总计行位于正确的位置。然后你可以在 SELECT 中使用它来区分这些行。

Mind your data types. Some columns may not be compatible with each other so you may need to cast.

Be careful with the ORDER BY, if you don't specify table aliases on the columns then it will sort by the final SELECT value, rather than the actual column value

实现 SQL 嵌套游标的最佳方法是什么

What is the best way to implement a SQL Nested Cursor

sql

tsql

database

sql-server

ssms