Merge branch 'master' of https://github.com/qiancai/docs

TOC.md

@@ -1057,6 +1057,7 @@
   - v7.2
     - [7.2.0-DMR](/releases/release-7.2.0.md)
   - v7.1
+    - [7.1.5](/releases/release-7.1.5.md)
     - [7.1.4](/releases/release-7.1.4.md)
     - [7.1.3](/releases/release-7.1.3.md)
     - [7.1.2](/releases/release-7.1.2.md)

functions-and-operators/cast-functions-and-operators.md

@@ -6,16 +6,64 @@ aliases: ['/docs/dev/functions-and-operators/cast-functions-and-operators/','/do
 
 # Cast Functions and Operators
 
-Cast functions and operators enable conversion of values from one data type to another. TiDB supports all of the [cast functions and operators](https://dev.mysql.com/doc/refman/5.7/en/cast-functions.html) available in MySQL 5.7.
-
-## List of cast functions and operators
+Cast functions and operators enable conversion of values from one data type to another. TiDB supports all of the [cast functions and operators](https://dev.mysql.com/doc/refman/8.0/en/cast-functions.html) available in MySQL 8.0.
 
 | Name                                     | Description                      |
 | ---------------------------------------- | -------------------------------- |
-| [`BINARY`](https://dev.mysql.com/doc/refman/8.0/en/cast-functions.html#operator_binary) | Cast a string to a binary string |
-| [`CAST()`](https://dev.mysql.com/doc/refman/8.0/en/cast-functions.html#function_cast) | Cast a value as a certain type   |
-| [`CONVERT()`](https://dev.mysql.com/doc/refman/8.0/en/cast-functions.html#function_convert) | Cast a value as a certain type   |
+| [`BINARY`](#binary) | Cast a string to a binary string |
+| [`CAST()`](#cast) | Cast a value as a certain type   |
+| [`CONVERT()`](#convert) | Cast a value as a certain type   |
 
 > **Note:**
 >
 > TiDB and MySQL display inconsistent results for `SELECT CAST(MeN AS CHAR)` (or its equivalent form `SELECT CONVERT(MeM, CHAR)`), where `MeN` represents a double-precision floating-point number in scientific notation. MySQL displays the complete numeric value when `-15 <= N <= 14` and the scientific notation when `N < -15` or `N > 14`. However, TiDB always displays the complete numeric value. For example, MySQL displays the result of `SELECT CAST(3.1415e15 AS CHAR)` as `3.1415e15`, while TiDB displays the result as `3141500000000000`.
+
+## BINARY
+
+The [`BINARY`](https://dev.mysql.com/doc/refman/8.0/en/cast-functions.html#operator_binary) operator has been deprecated since MySQL 8.0.27. It is recommended to use `CAST(... AS BINARY)` instead both in TiDB and MySQL.
+
+## CAST
+
+The [`CAST()`](https://dev.mysql.com/doc/refman/8.0/en/cast-functions.html#function_cast) function is used to cast an expression to a specific type.
+
+This function is also used to create [Multi-valued indexes](/sql-statements/sql-statement-create-index.md#multi-valued-indexes).
+
+Example:
+
+```sql
+SELECT CAST(0x54694442 AS CHAR);
+```
+
+```sql
++--------------------------+
+| CAST(0x54694442 AS CHAR) |
++--------------------------+
+| TiDB                     |
++--------------------------+
+1 row in set (0.0002 sec)
+```
+
+## CONVERT
+
+The [`CONVERT()`](https://dev.mysql.com/doc/refman/8.0/en/cast-functions.html#function_convert) function is used to convert between [character sets](/character-set-and-collation.md).
+
+Example:
+
+```sql
+SELECT CONVERT(0x616263 USING utf8mb4);
+```
+
+```sql
++---------------------------------+
+| CONVERT(0x616263 USING utf8mb4) |
++---------------------------------+
+| abc                             |
++---------------------------------+
+1 row in set (0.0004 sec)
+```
+
+## MySQL compatibility
+
+- TiDB does not support cast operations on `SPATIAL` types. For more information, see [#6347](https://github.com/pingcap/tidb/issues/6347).
+- TiDB does not support `AT TIME ZONE` for `CAST()`. For more information, see [#51742](https://github.com/pingcap/tidb/issues/51742).
+- `CAST(24 AS YEAR)` returns 2 digits in TiDB and 4 digits in MySQL. For more information, see [#29629](https://github.com/pingcap/tidb/issues/29629).

functions-and-operators/numeric-functions-and-operators.md

@@ -6,11 +6,11 @@ aliases: ['/docs/dev/functions-and-operators/numeric-functions-and-operators/','
 
 # Numeric Functions and Operators
 
-TiDB supports all of the [numeric functions and operators](https://dev.mysql.com/doc/refman/5.7/en/numeric-functions.html) available in MySQL 5.7.
+TiDB supports all of the [numeric functions and operators](https://dev.mysql.com/doc/refman/8.0/en/numeric-functions.html) available in MySQL 8.0.
 
 ## Arithmetic operators
 
-| Name                                                                                        | Description                       |
+| Name                                                                                          | Description                       |
 |:----------------------------------------------------------------------------------------------|:----------------------------------|
 | [`+`](https://dev.mysql.com/doc/refman/8.0/en/arithmetic-functions.html#operator_plus)        | Addition operator                 |
 | [`-`](https://dev.mysql.com/doc/refman/8.0/en/arithmetic-functions.html#operator_minus)       | Minus operator                    |
@@ -24,33 +24,37 @@ TiDB supports all of the [numeric functions and operators](https://dev.mysql.com
 
 | Name                                                                                                      | Description                                                       |
 |:----------------------------------------------------------------------------------------------------------|:------------------------------------------------------------------|
-| [`POW()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_pow)               | Return the argument raised to the specified power                 |
-| [`POWER()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_power)           | Return the argument raised to the specified power                 |
+| [`ABS()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_abs)               | Return the absolute value                                         |
+| [`ACOS()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_acos)             | Return the arc cosine                                             |
+| [`ASIN()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_asin)             | Return the arc sine                                               |
+| [`ATAN()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_atan)             | Return the arc tangent                                            |
+| [`ATAN2(), ATAN()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_atan2)   | Return the arc tangent of the two arguments                       |
+| [`CEIL()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_ceil)             | Return the smallest integer value not less than the argument      |
+| [`CEILING()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_ceiling)       | Return the smallest integer value not less than the argument      |
+| [`CONV()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_conv)             | Convert numbers between different number bases                    |
+| [`COS()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_cos)               | Return the cosine                                                 |
+| [`COT()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_cot)               | Return the cotangent                                              |
+| [`CRC32()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_crc32)           | Compute a cyclic redundancy check value                           |
+| [`DEGREES()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_degrees)       | Convert radians to degrees                                        |
 | [`EXP()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_exp)               | Raise to the power of                                             |
-| [`SQRT()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_sqrt)             | Return the square root of the argument                            |
+| [`FLOOR()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_floor)           | Return the largest integer value not greater than the argument    |
 | [`LN()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_ln)                 | Return the natural logarithm of the argument                      |
 | [`LOG()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_log)               | Return the natural logarithm of the first argument                |
-| [`LOG2()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_log2)             | Return the base-2 logarithm of the argument                       |
 | [`LOG10()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_log10)           | Return the base-10 logarithm of the argument                      |
+| [`LOG2()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_log2)             | Return the base-2 logarithm of the argument                       |
+| [`MOD()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_mod)               | Return the remainder                                              |
 | [`PI()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_pi)                 | Return the value of pi                                            |
-| [`TAN()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_tan)               | Return the tangent of the argument                                |
-| [`COT()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_cot)               | Return the cotangent                                              |
-| [`SIN()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_sin)               | Return the sine of the argument                                   |
-| [`COS()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_cos)               | Return the cosine                                                 |
-| [`ATAN()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_atan)             | Return the arc tangent                                            |
-| [`ATAN2(), ATAN()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_atan2)   | Return the arc tangent of the two arguments                       |
-| [`ASIN()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_asin)             | Return the arc sine                                               |
-| [`ACOS()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_acos)             | Return the arc cosine                                             |
+| [`POW()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_pow)               | Return the argument raised to the specified power                 |
+| [`POWER()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_power)           | Return the argument raised to the specified power                 |
 | [`RADIANS()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_radians)       | Return argument converted to radians                              |
-| [`DEGREES()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_degrees)       | Convert radians to degrees                                        |
-| [`MOD()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_mod)               | Return the remainder                                              |
-| [`ABS()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_abs)               | Return the absolute value                                         |
-| [`CEIL()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_ceil)             | Return the smallest integer value not less than the argument      |
-| [`CEILING()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_ceiling)       | Return the smallest integer value not less than the argument      |
-| [`FLOOR()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_floor)           | Return the largest integer value not greater than the argument    |
-| [`ROUND()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_round)           | Round the argument                                                |
 | [`RAND()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_rand)             | Return a random floating-point value                              |
+| [`ROUND()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_round)           | Round the argument                                                |
 | [`SIGN()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_sign)             | Return the sign of the argument                                   |
-| [`CONV()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_conv)             | Convert numbers between different number bases                    |
+| [`SIN()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_sin)               | Return the sine of the argument                                   |
+| [`SQRT()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_sqrt)             | Return the square root of the argument                            |
+| [`TAN()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_tan)               | Return the tangent of the argument                                |
 | [`TRUNCATE()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_truncate)     | Truncate to specified number of decimal places                    |
-| [`CRC32()`](https://dev.mysql.com/doc/refman/8.0/en/mathematical-functions.html#function_crc32)           | Compute a cyclic redundancy check value                           |
+
+## Related system variables
+
+[`div_precision_increment`](/system-variables.md#div_precision_increment-new-in-v800) is used to set the precision for the `/` operator.

functions-and-operators/string-functions.md

@@ -419,11 +419,85 @@ Output:
 
 ### [`ELT()`](https://dev.mysql.com/doc/refman/8.0/en/string-functions.html#function_elt)
 
-Return string at index number.
+The `ELT()` function returns the element at the index number.
+
+```sql
+SELECT ELT(3, 'This', 'is', 'TiDB');
+```
+
+```sql
++------------------------------+
+| ELT(3, 'This', 'is', 'TiDB') |
++------------------------------+
+| TiDB                         |
++------------------------------+
+1 row in set (0.00 sec)
+```
+
+The preceding example returns the third element, which is `'TiDB'`.
 
 ### [`EXPORT_SET()`](https://dev.mysql.com/doc/refman/8.0/en/string-functions.html#function_export-set)
 
-Return a string such that for every bit set in the value bits, you get an on string and for every unset bit, you get an off string.
+The `EXPORT_SET()` function returns a string that consists of a specified number (`number_of_bits`) of `on`/`off` values, optionally separated by `separator`. These values are based on whether the corresponding bit in the `bits` argument is `1`, where the first value corresponds to the rightmost (lowest) bit of `bits`.
+
+Syntax:
+
+```sql
+EXPORT_SET(bits, on, off, [separator[, number_of_bits]])
+```
+
+- `bits`: an integer representing the bit value.
+- `on`: the string to be returned if the corresponding bit is `1`.
+- `off`: the string to be returned if the corresponding bit is `0`.
+- `separator` (optional): the separator character in the result string.
+- `number_of_bits` (optional): the number of bits to be processed. If it is not set, `64` (the max size of bits) is used by default, which means that `bits` is treated as an unsigned 64-bit integer.
+
+Examples:
+
+In the following example, `number_of_bits` is set to `5`, resulting in 5 values, separated by `|`. Because only 3 bits are given, the other bits are considered unset. Therefore, setting `number_of_bits` to either `101` or `00101` results in the same output.
+
+```sql
+SELECT EXPORT_SET(b'101',"ON",'off','|',5);
+```
+
+```sql
++-------------------------------------+
+| EXPORT_SET(b'101',"ON",'off','|',5) |
++-------------------------------------+
+| ON|off|ON|off|off                   |
++-------------------------------------+
+1 row in set (0.00 sec)
+```
+
+In the following example, `bits` is set to `00001111`, `on` is set to `x`, and `off` is set to `_`. This causes the function to return `____` for the `0` bits and `xxxx` for the `1` bits. Therefore, when processing with the bits in `00001111` from right to left, the function returns `xxxx____`.
+
+```sql
+SELECT EXPORT_SET(b'00001111', 'x', '_', '', 8);
+```
+
+```sql
++------------------------------------------+
+| EXPORT_SET(b'00001111', 'x', '_', '', 8) |
++------------------------------------------+
+| xxxx____                                 |
++------------------------------------------+
+1 row in set (0.00 sec)
+```
+
+In the following example, `bits` is set to `00001111`, `on` is set to `x`, and `off` is set to `_`. This causes the function to return `x` for each `1` bit and `_` for each `0` bit. Therefore, when processing with the bits in `01010101` from right to left, the function returns `x_x_x_x_`.
+
+```sql
+SELECT EXPORT_SET(b'01010101', 'x', '_', '', 8);
+```
+
+```sql
++------------------------------------------+
+| EXPORT_SET(b'01010101', 'x', '_', '', 8) |
++------------------------------------------+
+| x_x_x_x_                                 |
++------------------------------------------+
+1 row in set (0.00 sec)
+```
 
 ### [`FIELD()`](https://dev.mysql.com/doc/refman/8.0/en/string-functions.html#function_field)