database_Leet code 2118. Build the Equation
+-------------+------+
| 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 has to follow the following rules: The LHS should contain all the terms.
The RHS should be zero.
Each term of the LHS should follow the format "sign factor X ^power" after removing the white spaces where: sign is either "+" or "-". factor is the absolute value of the factor.
power is the value of the power.
If the power is 1, do not add "^power".
For example, if power = 1 and factor = 3, the term will be "+3X".
If the power is 0, add neither "X" nor "^power".
For example, if power = 0 and factor = -3, the term will be "-3".
The powers in the RHS should be sorted in descending order.
Write an SQL query to build the equation.
The query result format is in the following example.
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 |
+-----------------+
主要用自联接，stuff for xml path 还有convert 0的情况没单独验证，后面有机会验证一下，太困了。
