LeetCode SQL - Pivot Table

Posted on Symbols count in article: 3.7k Reading time ≈ 3 mins.

1179. Reformat Department Table

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DROP TABLE IF EXISTS Department;
CREATE TABLE
    If NOT EXISTS Department (id INT, revenue INT, MONTH VARCHAR(5));
TRUNCATE TABLE Department;
INSERT INTO
    Department (id, revenue, MONTH)
VALUES
    ('1', '8000', 'Jan');
INSERT INTO
    Department (id, revenue, MONTH)
VALUES
    ('2', '9000', 'Jan');
INSERT INTO
    Department (id, revenue, MONTH)
VALUES
    ('3', '10000', 'Feb');
INSERT INTO
    Department (id, revenue, MONTH)
VALUES
    ('1', '7000', 'Feb');
INSERT INTO
    Department (id, revenue, MONTH)
VALUES
    ('1', '6000', 'Mar');
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/*Reformat the Department table
- Department PK: (id, month)

- SOLUTION: GROUP BY
 */
SELECT
    id,
    SUM(if (MONTH = 'Jan', revenue, NULL)) AS 'Jan_Revenue',
    SUM(if (MONTH = 'Feb', revenue, NULL)) AS 'Feb_Revenue',
    SUM(if (MONTH = 'Mar', revenue, NULL)) AS 'Mar_Revenue',
    SUM(if (MONTH = 'Apr', revenue, NULL)) AS 'Apr_Revenue',
    SUM(if (MONTH = 'May', revenue, NULL)) AS 'May_Revenue',
    SUM(if (MONTH = 'Jun', revenue, NULL)) AS 'Jun_Revenue',
    SUM(if (MONTH = 'Jul', revenue, NULL)) AS 'Jul_Revenue',
    SUM(if (MONTH = 'Aug', revenue, NULL)) AS 'Aug_Revenue',
    SUM(if (MONTH = 'Sep', revenue, NULL)) AS 'Sep_Revenue',
    SUM(if (MONTH = 'Oct', revenue, NULL)) AS 'Oct_Revenue',
    SUM(if (MONTH = 'Nov', revenue, NULL)) AS 'Nov_Revenue',
    SUM(if (MONTH = 'Dec', revenue, NULL)) AS 'Dec_Revenue'
FROM
    Department
GROUP BY
    id;

Dynamic pivot table (not available on LeetCode):

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select @sql = null;
select group_concat(distinct concat("sum(if(month = '", month, "', revenue, null)) as ", month, "_Revenue")) from Department
into @sql;

select concat("select id, ", @sql, " from Department group by 1")
into @sql;

prepare stmt from @sql;
execute stmt;
deallocate prepare stmt;

2252. Dynamic Pivoting of a Table

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DROP TABLE if EXISTS Products;
CREATE TABLE
    If NOT EXISTS Products (product_id INT, store VARCHAR(8), price INT);
TRUNCATE TABLE Products;
INSERT INTO
    Products (product_id, store, price)
VALUES
    ('1', 'Shop', '110');
INSERT INTO
    Products (product_id, store, price)
VALUES
    ('1', 'LC_Store', '100');
INSERT INTO
    Products (product_id, store, price)
VALUES
    ('2', 'Nozama', '200');
INSERT INTO
    Products (product_id, store, price)
VALUES
    ('2', 'Souq', '190');
INSERT INTO
    Products (product_id, store, price)
VALUES
    ('3', 'Shop', '1000');
INSERT INTO
    Products (product_id, store, price)
VALUES
    ('3', 'Souq', '1900');
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create procedure PivotProducts()
begin
    set session group_concat_max_len = 1000000; # default is 1024
    
  set @sql = null;
  select group_concat(
    distinct concat(
      'sum(if(store = "', store, '", price, null)) as ', store
    )
  )
  into @sql
  from Products;

  set @sql = concat('select product_id, ', @sql, ' from Products group by 1 order by null');

  prepare stmt from @sql;
  execute stmt;
  deallocate prepare stmt;
end

For MySQLWorkbench test:

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drop procedure if exists PivotProducts;

delimiter //

create procedure PivotProducts()
begin
  set session group_concat_max_len = 1000000; # default is 1024

  set @sql = null;
  select group_concat(
    distinct concat(
      'sum(if(store = "', store, '", price, null)) as ', store
    ) separator ','
  )
  into @sql
  from Products;

  set @sql = concat('select product_id, ', @sql, ' from Products group by 1');

  prepare stmt from @sql;
  execute stmt;
  deallocate prepare stmt;
end //

delimiter ;

call PivotProducts();