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题目描述
写一个 SQL 查询, 以计算表 Expressions 中的布尔表达式.
返回的结果表没有顺序要求.
查询结果格式如下例所示.
题解
select e.left_operand, operator, e.right_operand,
case
when a.value < b.value and operator = '<' then "true"
when a.value > b.value and operator = '>' then "true"
when a.value = b.value and operator = '=' then "true"
else "false"
end as value
from expressions e
inner join variables a on e.left_operand = a.name
inner join variables b on e.right_operand = b.name