How do you convert a parent-child (adjacency) table to a nested set using PHP and MySQL?

Question

I\'ve spent the last few hours trying to find the solution to this question online. I\'ve found plenty of examples on how to convert from nested set to adjacency... but few

Answer 1

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*)"