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Add example in docs

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docs/en/sql-reference/data-types/newjson.md
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@ -630,6 +630,28 @@ SELECT arrayJoin(distinctJSONPathsAndTypes(json)) FROM s3('s3://clickhouse-publi
└─arrayJoin(distinctJSONPathsAndTypes(json))──────────────────┘
```
## ALTER MODIFY COLUMN to JSON type
It's possible to alter an existing table and change the type of the column to the new `JSON` type. Right now only alter from `String` type is supported.
**Example**
```sql
CREATE TABLE test (json String) ENGINE=MergeTree ORDeR BY tuple();
INSERT INTO test VALUES ('{"a" : 42}'), ('{"a" : 43, "b" : "Hello"}'), ('{"a" : 44, "b" : [1, 2, 3]}')), ('{"c" : "2020-01-01"}');
ALTER TABLE test MODIFY COLUMN json JSON;
SELECT json, json.a, json.b, json.c FROM test;
```
```text
┌─json─────────────────────────┬─json.a─┬─json.b──┬─json.c─────┐
1. │ {"a":"42"} │ 42 │ ᴺᵁᴸᴸ │ ᴺᵁᴸᴸ │
2. │ {"a":"43","b":"Hello"} │ 43 │ Hello │ ᴺᵁᴸᴸ │
3. │ {"a":"44","b":["1","2","3"]} │ 44 │ [1,2,3] │ ᴺᵁᴸᴸ │
4. │ {"c":"2020-01-01"} │ ᴺᵁᴸᴸ │ ᴺᵁᴸᴸ │ 2020-01-01 │
└──────────────────────────────┴────────┴─────────┴────────────┘
```
## Tips for better usage of the JSON type
Before creating `JSON` column and loading data into it, consider the following tips: