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Problem

Table: Terms

+-------------+------+
| Column Name | Type |
+-------------+------+
| power       | int  |
| factor      | int  |
+-------------+------+
power is the primary key column for this table.
Each row of this table contains information about one term of the equation.
power is an integer in the range [0, 100].
factor is an integer in the range [-100, 100] and cannot be zero.

You have a very powerful program that can solve any equation of one variable in the world. The equation passed to the program must be formatted as follows:

The left-hand side (LHS) should contain all the terms. The right-hand side (RHS) should be zero. Each term of the LHS should follow the format “X^" where:

is either "+" or "-". is the absolute value of the factor. is the value of the power. If the power is 1, do not add "^". For example, if power = 1 and factor = 3, the term will be "+3X". If the power is 0, add neither "X" nor "^". For example, if power = 0 and factor = -3, the term will be "-3". The powers in the LHS should be sorted in descending order. Write an SQL query to build the equation. The query result format is in the following example. Example 1: ``` Input: Terms table: +-------+--------+ | power | factor | +-------+--------+ | 2 | 1 | | 1 | -4 | | 0 | 2 | +-------+--------+ Output: +--------------+ | equation | +--------------+ | +1X^2-4X+2=0 | +--------------+ ``` Example 2: ``` Input: Terms table: +-------+--------+ | power | factor | +-------+--------+ | 4 | -4 | | 2 | 1 | | 1 | -1 | +-------+--------+ Output: +-----------------+ | equation | +-----------------+ | -4X^4+1X^2-1X=0 | +-----------------+ ``` ## Code ```sql select concat(group_concat(term order by power desc separator ''), '=0') as equation from ( select CONCAT(case when factor > 0 then '+' else '' end, factor, case when power = 0 then '' else 'X' end, case when power = 0 or power = 1 then '' else '^' end, case when power = 0 or power = 1 then '' else power end ) term, power from terms order by power desc) t; ```