> For the complete documentation index, see [llms.txt](https://imhuay.gitbook.io/studies/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://imhuay.gitbook.io/studies/notes/_archives/2023/01/sql-chang-yong-cha-xun-ji-lu.md).

# Hive/Spark SQL 常用查询记录

![last modify](https://img.shields.io/static/v1?label=last%20modify\&message=2023-02-19%2020%3A11%3A02\&color=yellowgreen\&style=flat-square)

> ***Keywords**: Hive/Spark SQL*

## 聚合操作

###

## 个人习惯

### 集合字段 `map/json`

* 作为一个额外字段, 可以把新的字段统一放到这里, 防止频繁修改表;

```sql
-- CREATE
CREATE TABLE db.table (
    ...
    , `features`    map < string, double >  COMMENT 'features'
    , `info_json`   string                  COMMENT 'extra info'
) COMMENT 'xxx 特征表'

-- INSERT

INSERT OVERWRITE TABLE db.table
SELECT ...
    , map(
          'f1', f1_double
        , 'f2', f2_int
        , ...
      ) AS features
    , concat('{'
        , '"k1":', k1_int, ','  -- 注意 key 要双引号
        , '"k2":', k2
      , '}') AS info_json
FROM ...

-- SELECT
SELECT ...
    ,  features['f1'] AS f1
    ,  features['f2'] AS f2
    ,  get_json_object(info_json, '$.k1') AS k1
    ,  get_json_object(info_json, '$.k2') AS k2
FROM db.table
```

### 小词表

```sql
```


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