fix-broken-external-links (#5971)

functions-and-operators/aggregate-group-by-functions.md

@@ -9,17 +9,17 @@ This document describes details about the supported aggregate functions in TiDB.
 
 ## Supported aggregate functions
 
-This section describes the supported MySQL group (aggregate) functions in TiDB.
+This section describes the supported MySQL `GROUP BY` aggregate functions in TiDB.
 
 | Name                                                                                                        | Description                                       |
 |:--------------------------------------------------------------------------------------------------------------|:--------------------------------------------------|
-| [`COUNT()`](https://dev.mysql.com/doc/refman/5.7/en/group-by-functions.html#function_count)                   | Return a count of the number of rows returned     |
-| [`COUNT(DISTINCT)`](https://dev.mysql.com/doc/refman/5.7/en/group-by-functions.html#function_count-distinct)  | Return the count of a number of different values  |
-| [`SUM()`](https://dev.mysql.com/doc/refman/5.7/en/group-by-functions.html#function_sum)                       | Return the sum                                    |
-| [`AVG()`](https://dev.mysql.com/doc/refman/5.7/en/group-by-functions.html#function_avg)                       | Return the average value of the argument          |
-| [`MAX()`](https://dev.mysql.com/doc/refman/5.7/en/group-by-functions.html#function_max)                       | Return the maximum value                          |
-| [`MIN()`](https://dev.mysql.com/doc/refman/5.7/en/group-by-functions.html#function_min)                       | Return the minimum value                          |
-| [`GROUP_CONCAT()`](https://dev.mysql.com/doc/refman/5.7/en/group-by-functions.html#function_group-concat)     | Return a concatenated string                     |
+| [`COUNT()`](https://dev.mysql.com/doc/refman/5.7/en/aggregate-functions.html#function_count)                   | Return a count of the number of rows returned     |
+| [`COUNT(DISTINCT)`](https://dev.mysql.com/doc/refman/5.7/en/aggregate-functions.html#function_count-distinct)  | Return the count of a number of different values  |
+| [`SUM()`](https://dev.mysql.com/doc/refman/5.7/en/aggregate-functions.html#function_sum)                       | Return the sum                                    |
+| [`AVG()`](https://dev.mysql.com/doc/refman/5.7/en/aggregate-functions.html#function_avg)                       | Return the average value of the argument          |
+| [`MAX()`](https://dev.mysql.com/doc/refman/5.7/en/aggregate-functions.html#function_max)                       | Return the maximum value                          |
+| [`MIN()`](https://dev.mysql.com/doc/refman/5.7/en/aggregate-functions.html#function_min)                       | Return the minimum value                          |
+| [`GROUP_CONCAT()`](https://dev.mysql.com/doc/refman/5.7/en/aggregate-functions.html#function_group-concat)     | Return a concatenated string                     |
 | [`VARIANCE()`, `VAR_POP()`](https://dev.mysql.com/doc/refman/5.7/en/aggregate-functions.html#function_var-pop) | Return the population standard variance|
 | [`STD()`，`STDDEV()`，`STDDEV_POP`](https://dev.mysql.com/doc/refman/5.7/en/aggregate-functions.html#function_std) | Return the population standard deviation |
 | [`VAR_SAMP()`](https://dev.mysql.com/doc/refman/5.7/en/aggregate-functions.html#function_var-samp) | Return the sample variance |

functions-and-operators/expressions-pushed-down.md

@@ -144,23 +144,43 @@ tidb> explain select * from t where a < 2 and a > 2;
 | IS FALSE | isfalse |
 
 [json_extract]: https://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html#function_json-extract
+
 [json_short_extract]: https://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html#operator_json-column-path
+
 [json_short_extract_unquote]: https://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html#operator_json-inline-path
+
 [json_unquote]: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-unquote
+
 [json_type]: https://dev.mysql.com/doc/refman/5.7/en/json-attribute-functions.html#function_json-type
+
 [json_set]: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-set
+
 [json_insert]: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-insert
+
 [json_replace]: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-replace
+
 [json_remove]: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-remove
+
 [json_merge]: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-merge
+
 [json_merge_preserve]: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-merge-preserve
+
 [json_object]: https://dev.mysql.com/doc/refman/5.7/en/json-creation-functions.html#function_json-object
+
 [json_array]: https://dev.mysql.com/doc/refman/5.7/en/json-creation-functions.html#function_json-array
+
 [json_keys]: https://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html#function_json-keys
+
 [json_length]: https://dev.mysql.com/doc/refman/5.7/en/json-attribute-functions.html#function_json-length
+
 [json_valid]: https://dev.mysql.com/doc/refman/5.7/en/json-attribute-functions.html#function_json-valid
+
 [json_quote]: https://dev.mysql.com/doc/refman/5.7/en/json-creation-functions.html#function_json-quote
+
 [json_contains]: https://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html#function_json-contains
+
 [json_contains_path]: https://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html#function_json-contains-path
+
 [json_arrayagg]: https://dev.mysql.com/doc/refman/5.7/en/group-by-functions.html#function_json-arrayagg
+
 [json_depth]: https://dev.mysql.com/doc/refman/5.7/en/json-attribute-functions.html#function_json-depth

functions-and-operators/json-functions.md

@@ -83,27 +83,51 @@ The following JSON functions are unsupported in TiDB. You can track the progress
 * [JSON Data Type](/data-type-json.md)
 
 [json_extract]: https://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html#function_json-extract
+
 [json_short_extract]: https://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html#operator_json-column-path
+
 [json_short_extract_unquote]: https://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html#operator_json-inline-path
+
 [json_unquote]: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-unquote
+
 [json_type]: https://dev.mysql.com/doc/refman/5.7/en/json-attribute-functions.html#function_json-type
+
 [json_set]: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-set
+
 [json_insert]: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-insert
+
 [json_replace]: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-replace
+
 [json_remove]: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-remove
+
 [json_merge]: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-merge
+
 [json_merge_preserve]: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-merge-preserve
+
 [json_object]: https://dev.mysql.com/doc/refman/5.7/en/json-creation-functions.html#function_json-object
+
 [json_array]: https://dev.mysql.com/doc/refman/5.7/en/json-creation-functions.html#function_json-array
+
 [json_keys]: https://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html#function_json-keys
+
 [json_length]: https://dev.mysql.com/doc/refman/5.7/en/json-attribute-functions.html#function_json-length
+
 [json_valid]: https://dev.mysql.com/doc/refman/5.7/en/json-attribute-functions.html#function_json-valid
+
 [json_quote]: https://dev.mysql.com/doc/refman/5.7/en/json-creation-functions.html#function_json-quote
+
 [json_contains]: https://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html#function_json-contains
+
 [json_contains_path]: https://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html#function_json-contains-path
-[json_arrayagg]: https://dev.mysql.com/doc/refman/5.7/en/group-by-functions.html#function_json-arrayagg
+
+[json_arrayagg]: https://dev.mysql.com/doc/refman/5.7/en/aggregate-functions.html#function_json-arrayagg
+
 [json_depth]: https://dev.mysql.com/doc/refman/5.7/en/json-attribute-functions.html#function_json-depth
+
 [json_search]: https://dev.mysql.com/doc/refman/5.7/en/json-search-functions.html#function_json-search
+
 [json_append]: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-append
+
 [json_array_append]: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-array-append
+
 [json_array_insert]: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-array-insert