# SQL  and PySpark functions

1. Aggregation function
2. Window functions
3. Create /  Drop tables
4. Create / Drop database
5. Insert and modify 
6. Other Useful PySpark functions

   1. **lit**(value).alias(column\_name): 用于添加新的column到table而column的值=value 或者 value 是原来的table的某列的值， 之后再用alias重新命名
   2. **pivot**(column\_name) .count() 用于把某一列的类别值展开变成multi-onehot的形式

```
tmp.groupBy("movieId").pivot("splitted_genres").count().fillna(0).show()
```


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