发布于广东 统计每种性别的人数
https://www.nowcoder.com/practice/f04189f92f8d4f6fa0f383d413af7cb8
SELECT SUBSTRING_INDEX(profile,',',-1) gender, count(1) number FROM user_submit group by SUBSTRING_INDEX(profile,',',-1)
主要考字符串的拆分SUBSTRING_INDEX与分组求和
SQL练习
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const flattern = (obj) => {
const res = {};
const dfs = (curr, path) => {
if(typeof curr === 'object' && curr !== null) {
const isArray = Array.isArray(curr);
for(let key in curr) {
const newPath = path ? isArray ? `${path}[${key}]` : `${path}.${key}` : key;
dfs(curr[key], newPath);
}
} else {
res[path] = curr
}
}
dfs(obj);
return res;
}
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