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Formatted question description: https://leetcode.ca/all/2480.html
2480. Form a Chemical Bond
Description
Table: Elements
+-------------+---------+
| Column Name | Type |
+-------------+---------+
| symbol | varchar |
| type | enum |
| electrons | int |
+-------------+---------+
symbol is the primary key for this table.
Each row of this table contains information of one element.
type is an ENUM of type ('Metal', 'Nonmetal', 'Noble')
- If type is Noble, electrons is 0.
- If type is Metal, electrons is the number of electrons that one atom of this element can give.
- If type is Nonmetal, electrons is the number of electrons that one atom of this element needs.
Two elements can form a bond if one of them is 'Metal' and the other is 'Nonmetal'.
Write an SQL query to find all the pairs of elements that can form a bond.
Return the result table in any order.
The query result format is in the following example.
Example 1:
Input: Elements table: +--------+----------+-----------+ | symbol | type | electrons | +--------+----------+-----------+ | He | Noble | 0 | | Na | Metal | 1 | | Ca | Metal | 2 | | La | Metal | 3 | | Cl | Nonmetal | 1 | | O | Nonmetal | 2 | | N | Nonmetal | 3 | +--------+----------+-----------+ Output: +-------+----------+ | metal | nonmetal | +-------+----------+ | La | Cl | | Ca | Cl | | Na | Cl | | La | O | | Ca | O | | Na | O | | La | N | | Ca | N | | Na | N | +-------+----------+ Explanation: Metal elements are La, Ca, and Na. Nonmeal elements are Cl, O, and N. Each Metal element pairs with a Nonmetal element in the output table.
Solutions
-
# Write your MySQL query statement below SELECT a.symbol AS metal, b.symbol AS nonmetal FROM Elements AS a, Elements AS b WHERE a.type = 'Metal' AND b.type = 'Nonmetal';