Adjacency table to nested set conversion - mysql

Question

I need to convert an adjacency list to nested set in MySql. I have found only one resource over the internet to convert an adjacency list into a nested set using mysql(http://data.bangtech.com/sql/nested_set_treeview.htm). The code is also on the same webpage.
CREATE TABLE test.Tree
(emp CHAR(10) NOT NULL,
boss CHAR(10));
CREATE TABLE test.Personnel(
emp CHAR(20) PRIMARY KEY,
boss CHAR(20) REFERENCES Personnel(emp),
salary DECIMAL(6,2) NOT NULL
);
INSERT INTO test.Personnel VALUES ('jerry', 'NULL',1000.00);
INSERT INTO test.Personnel VALUES ('Bert', 'jerry',900.00);
INSERT INTO test.Personnel VALUES ('chuck', 'jerry',900.00);
INSERT INTO test.Personnel VALUES ('donna', 'chuck',800.00);
INSERT INTO test.Personnel VALUES ('eddie', 'chuck',700.00);
INSERT INTO test.Personnel VALUES ('fred', 'chuck',600.00);
INSERT INTO test.Tree
SELECT emp, boss FROM test.Personnel;
I make the Tree table from Personnel table. Tree table has the boss-employee hierarchy. This is an adjacency list. To convert it to the nest set, I applied this code.
BEGIN ATOMIC
DECLARE counter integer;
DECLARE max_counter integer;
DECLARE current_top integer;
SET counter = 2;
SET max_counter = 2 * (SELECT COUNT(*) FROM test.Tree);
SET current_top = 1;
INSERT INTO test.Stack
SELECT 1, emp, 1, NULL
FROM test.Tree
WHERE boss IS NULL;
DELETE FROM test.Tree
WHERE boss IS NULL;
WHILE counter <=(max_counter - 2)
LOOP IF EXISTS (SELECT * FROM test.Stack AS S1, test.Tree AS T1
WHERE S1.emp = T1.boss AND S1.stack_top = current_top)
THEN
BEGIN -- push when top has subordinates, set lft value
INSERT INTO test.Stack
SELECT (current_top + 1), MIN(T1.emp), counter, NULL
FROM test.Stack AS S1, test.Tree AS T1
WHERE S1.emp = T1.boss
AND S1.stack_top = current_top;
DELETE FROM test.Tree
WHERE emp = (SELECT emp
FROM test.Stack
WHERE stack_top = current_top + 1);
SET counter = counter + 1;
SET current_top = current_top + 1;
END
ELSE
BEGIN -- pop the stack and set rgt value
UPDATE test.Stack
SET rgt = counter,
stack_top = -stack_top -- pops the stack
WHERE stack_top = current_top
SET counter = counter + 1;
SET current_top = current_top - 1;
END IF;
END LOOP;
END;
MySQL workbench shows several syntax errors which I could not remove.
I am familiar with only very basic operations of mysql so could not debug the code on my own. How to remove all these errors? Plz Help.
The second source I found to do the above operation is http://www.sqlservercentral.com/articles/Hierarchy/94040/ but the code is in T Sql and I don't have enough skills to translate it to MySQL.

Answer 1

You should put NULL and not 'NULL' in the line
INSERT INTO test.Personnel VALUES ('jerry', 'NULL',1000.00);
Correct version:
INSERT INTO test.Personnel VALUES ('jerry', NULL, 1000.00);

Answer 2

Use Bash:
Bash converting:
# SQL command to fetch necessary fields, output it to text archive "tree"
SELECT id, parent_id, name FROM projects;
# Make a list "id|parentid|name" and sort by name
cat tree |
cut -d "|" -f 2-4 |
sed 's/^ *//;s/ *| */|/g' |
sort -t "|" -k 3,3 > list
# Creates the parenthood chain on second field
while IFS="|" read i p o
do
l=$p
while [[ "$p" != "NULL" ]]
do
p=$(grep -w "^$p" list | cut -d "|" -f 2)
l="$l,$p"
done
echo "$i|$l|$o"
done < list > listpar
# Creates left and right on 4th and 5th fields for interaction 0
let left=0
while IFS="|" read i l o
do
let dif=$(grep "\b$i,NULL|" listpar | wc -l)*2+1
let right=++left+dif
echo "$i|$l|$o|$left|$right"
let left=right
done <<< "$(grep "|NULL|" listpar)" > i0
# The same for following interactions
n=0
while [ -s i$n ]
do
while IFS="|" read i l nil left nil
do
grep "|$i,$l|" listpar |
while IFS="|" read i l o
do
let dif=$(grep "\b$i,$l|" listpar | wc -l)*2+1
let right=++left+dif
echo "$i|$l|$o|$left|$right"
let left=right
done
done < i$n > i$((++n))
done
# Show concatenated
cat i*|sort -t"|" -k 4n
# SQL commands
while IFS="|" read id nil nil left right
do
echo "UPDATE projects SET lft=$left, rgt=$right WHERE id=$id;"
done <<< "$(cat i*)"