SQL Server stored procedure: iterate through table, compare values, insert to different table on value change - sql

Question

I can't tell whether my particular situation has already been covered given the titles of other questions, so apologies if an answer already exists.
I have a database that records values as strings, and another table that records runs of particular types within those values.
I require a stored procedure that iterates through the values (I understand this is related to the concept of Cursors), recording each value to temporary tables to control the count for a particular run type (odd/even numbers, for example, or vowels/consonants). When a given value indicates that a particular type of run has stopped (i.e. an odd number has stopped a run of even numbers and vice versa), the run is counted, the count is inserted into a runs table with a related type value (0 = odd/even, 1 = vowel/consonant etc.), the temporary table contents are deleted, and the value that caused the table count/clear is inserted to the temp table.
As I am completely new to stored procedures, I don't know exactly how to structure this kind of procedure, and the examples I've found don't:
Describe how to implement Cursors in a straightforward, understandable manner
Provide insights into comparisons between a given value and a stored comparison value
Allow for recognition of changes to an established pattern to initiate a section of a procedure
Let me know if any of this needs clarifying.
EDIT:
Version in use: MS SQL Server 2012
table structure for the raw values:
ID: Int PK AI
DateTimeStamp: Datetime
SelectedValue: Char(2)
UserId: Int
table structure for value runs:
ID: Int PK AI
DateTimeStamp: Datetime
Type: Int
Run: Int
Sample data: [following presented as comma-delimited string for brevity, input by one user]
e, 00, 1, t, r, 2, 4, 3, 5, 7, a, i, w, q, u, o, 23, 25, 24, 36, 12, e ...
groups would be:
vowels/consonants
even numbers/odd numbers
00
numbers under/over 20
numbers/letters
From the above, the runs are:
e (vowels/consonants: vowels)
e (numbers/letters: letters)
00 (00)
1 (odd/even: odd)
1 (numbers/letters: numbers)
t, r (vowels/consonants: consonants)
t, r (numbers/letters: letters)
2, 4 (odd/even: even)
3, 5, 7 (odd/even: odd)
2, 4, 3, 5, 7 (numbers/letters: numbers)
a, i (vowels/consonants: vowels)
w, q (vowels/consonants: consonants)
a, i, w, q, u, o (numbers/letters: letters)
1, 2, 4, 3, 5, 7 (under/over 20: under 20)
23, 25 (odd/even: odd)
23, 25, 24, 36 (under/over 20: over 20)
24, 36, 12 (odd/even: even)
u, o, e (vowels/consonants: vowels)
Which would make entries to the runs table as
Type: vowels/consonants, run: 1
Type: numbers/letters, run: 1
Type: 00, run: 1
Type: odd/even, run: 1
Type: numbers/letters, run: 1
Type: odd/even, run: 2
Type: odd/even, run: 3
Type: numbers/letters, run: 5
Type: vowels/consonants, run: 2
Type: vowels/consonants, run: 2
Type: numbers/letters, run: 6
Type: under/over 20, run: 6
Type: odd/even, run: 2
Type: under/over 20, run: 4
Type: odd/even, run: 3
Type: vowels/consonants, run: 3

Answer 1

EDIT Updated based on clarification of the original question.
This might not be the cleanest solution, but it should get you started:
WITH cteClassifications (ID, GroupNo, Type, Description) As
(
-- Vowels:
SELECT
ID,
1,
1,
'Vowels'
FROM
RawData
WHERE
SelectedValue In ('a', 'e', 'i', 'o', 'u')
UNION ALL
-- Consonants:
SELECT
ID,
1,
2,
'Consonants'
FROM
RawData
WHERE
SelectedValue Between 'a' And 'z'
And
SelectedValue Not In ('a', 'e', 'i', 'o', 'u')
UNION ALL
-- Even numbers:
SELECT
ID,
2,
1,
'Even numbers'
FROM
RawData
WHERE
SelectedValue != '00'
And
SelectedValue Not Between 'a' And 'z'
And
(TRY_PARSE(SelectedValue As tinyint) & 1) = 0
UNION ALL
-- Odd numbers:
SELECT
ID,
2,
2,
'Odd numbers'
FROM
RawData
WHERE
SelectedValue != '00'
And
SelectedValue Not Between 'a' And 'z'
And
(TRY_PARSE(SelectedValue As tinyint) & 1) = 1
UNION ALL
-- "00":
SELECT
ID,
3,
1,
'"00"'
FROM
RawData
WHERE
SelectedValue = '00'
UNION ALL
-- Numbers under 20:
SELECT
ID,
4,
1,
'Numbers under 20'
FROM
RawData
WHERE
SelectedValue != '00'
And
SelectedValue Not Between 'a' And 'z'
And
TRY_PARSE(SelectedValue As tinyint) < 20
UNION ALL
-- Numbers over 20:
SELECT
ID,
4,
2,
'Numbers over 20'
FROM
RawData
WHERE
SelectedValue != '00'
And
SelectedValue Not Between 'a' And 'z'
And
TRY_PARSE(SelectedValue As tinyint) > 20
UNION ALL
-- Numbers:
SELECT
ID,
5,
1,
'Numbers'
FROM
RawData
WHERE
SelectedValue != '00'
And
SelectedValue Not Between 'a' And 'z'
And
TRY_PARSE(SelectedValue As tinyint) Is Not Null
UNION ALL
-- Letters:
SELECT
ID,
5,
2,
'Letters'
FROM
RawData
WHERE
SelectedValue Between 'a' And 'z'
),
cteOrderedClassifications (ID, GroupNo, Type, Description, PrevType, RN) As
(
SELECT
ID,
GroupNo,
Type,
Description,
LAG(Type, 1, 0) OVER (PARTITION BY GroupNo ORDER BY ID),
ROW_NUMBER() OVER (PARTITION BY GroupNo ORDER BY ID)
FROM
cteClassifications
),
cteGroupedClassifications (ID, GroupNo, Type, Description, RN, ORN) As
(
SELECT
ID,
GroupNo,
Type,
Description,
RN,
RN
FROM
cteOrderedClassifications As C
WHERE
Type != PrevType
UNION ALL
SELECT
C.ID,
G.GroupNo,
G.Type,
G.Description,
G.RN,
C.RN
FROM
cteGroupedClassifications As G
INNER JOIN cteOrderedClassifications As C
ON C.GroupNo = G.GroupNo
And C.Type = G.Type
And C.RN = G.ORN + 1
),
cteRuns (ID, GroupNo, Type, Description, RN, Run) As
(
SELECT
Min(ID),
GroupNo,
Type,
MAX(Description),
RN,
Count(1)
FROM
cteGroupedClassifications
GROUP BY
GroupNo,
Type,
RN
)
SELECT
ROW_NUMBER() OVER (ORDER BY ID) As ID,
GroupNo,
Type,
Description,
Run
FROM
cteRuns
ORDER BY
ID
;
Once you're happy that the query is working, you can replace the final SELECT with an INSERT INTO Runs (ID, Type, Run) SELECT ID, Type, Run FROM cteFinalRuns to populate the table in a single pass.
SQL Fiddle example