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new 459a408b488 Add print docs of all types (#3011)
459a408b488 is described below
commit 459a408b4880b7bc286436a67c7d8e381d1f9d86
Author: zclllyybb <[email protected]>
AuthorDate: Mon Oct 27 12:48:29 2025 +0800
Add print docs of all types (#3011)
## Versions
- [x] dev
- [ ] 3.x
- [ ] 2.1
- [ ] 2.0
## Languages
- [x] Chinese
- [x] English
## Docs Checklist
- [ ] Checked by AI
- [ ] Test Cases Built
---
.../sql-data-types/conversion/cast-to-string.md | 329 +++++++++++++++++++++
.../sql-data-types/conversion/cast-to-string.md | 329 +++++++++++++++++++++
sidebars.json | 1 +
3 files changed, 659 insertions(+)
diff --git
a/docs/sql-manual/basic-element/sql-data-types/conversion/cast-to-string.md
b/docs/sql-manual/basic-element/sql-data-types/conversion/cast-to-string.md
new file mode 100644
index 00000000000..eb46aa402ad
--- /dev/null
+++ b/docs/sql-manual/basic-element/sql-data-types/conversion/cast-to-string.md
@@ -0,0 +1,329 @@
+---
+{
+ "title": "Cast to String (Output)",
+ "language": "en"
+}
+---
+
+## Boolean
+
+If the value is true, returns 1. Otherwise returns 0.
+
+```sql
+mysql> select cast(true as string) , cast(false as string);
++----------------------+-----------------------+
+| cast(true as string) | cast(false as string) |
++----------------------+-----------------------+
+| 1 | 0 |
++----------------------+-----------------------+
+```
+
+## Integer
+
+Converts according to the decimal format of the numeric value, without prefix
0. Non-negative numbers have no '+' prefix, negative numbers have '-' prefix.
+
+Example:
+
+```sql
+select cast(cast("123" as int) as string) as str_value;
++-----------+
+| str_value |
++-----------+
+| 123 |
++-----------+
+
+select cast(cast("-2147483648" as int) as string) as str_value;
++-------------+
+| str_value |
++-------------+
+| -2147483648 |
++-------------+
+```
+
+## Float
+
+Detailed rules for converting float values to strings:
+
+1. **Special Value Handling**:
+
+ * `NaN` (Not a Number) is converted to the string "NaN"
+
+ * `Infinity` is converted to the string "Infinity"
+
+ * `-Infinity` is converted to the string "-Infinity"
+
+2. **Sign Handling**:
+
+ * Negative numbers have a '-' prefix
+
+ * Positive numbers have no sign prefix
+
+ * Special handling for zero values:
+
+ * `-0.0` is converted to "-0"
+
+ * `+0.0` is converted to "0"
+
+3. **Format Rules**:
+
+ * Uses C printf 'g' format specifier semantics (refer to
https://en.cppreference.com/w/c/io/fprintf) to convert floating-point numbers
to decimal or scientific notation, depending on the value and the number of
significant digits. The number of significant digits is set to 7. If the
exponent X of the 'e' style conversion result is:
+
+ * If 7 > X >= -4, then the result uses decimal notation
+
+ * Otherwise, uses scientific notation with a maximum of 6 significant
digits after the decimal point
+
+ * Removes trailing zeros after the decimal point
+
+ * If there are no digits after the decimal point, removes the decimal point
+
+Example:
+
+| float | string | comment
|
+| -------------- | --------------- |
---------------------------------------------- |
+| 123.456 | "123.456" |
|
+| 1234567 | "1234567" |
|
+| 123456.12345 | "123456.1" | e < 7, uses scientific notation, 7
significant digits |
+| 12345678.12345 | "1.234568e+07" | e >= 7, uses scientific notation, 7
significant digits |
+| 0.0001234567 | "0.0001234567" | e >= -4, does not use scientific notation
|
+| -0.0001234567 | "-0.0001234567" | e >= -4, does not use scientific notation
|
+| 0.00001234567 | "1.234567e-05" | e < -4, uses scientific notation
|
+| 123.456000 | "123.456" | Remove trailing zeros
|
+| 123.000 | "123" | Remove decimal point
|
+| 0.0 | "0" |
|
+| -0.0 | "-0" | Negative zero
|
+| NaN | "NaN" |
|
+| Infinity | "Infinity" |
|
+| -Infinity | "-Infinity" |
|
+
+## Double
+
+Detailed rules for converting double values to strings:
+
+1. **Special Value Handling**:
+
+ * `NaN` (Not a Number) is converted to the string "NaN"
+
+ * `Infinity` is converted to the string "Infinity"
+
+ * `-Infinity` is converted to the string "-Infinity"
+
+2. **Sign Handling**:
+
+ * Negative numbers have a '-' prefix
+
+ * Positive numbers have no sign prefix
+
+ * Special handling for zero values:
+
+ * `-0.0` is converted to "-0"
+
+ * `+0.0` is converted to "0"
+
+3. **Format Rules**:
+
+ * Uses C printf 'g' format specifier semantics (refer to
https://en.cppreference.com/w/c/io/fprintf) to convert floating-point numbers
to decimal or scientific notation, depending on the value and the number of
significant digits. The number of significant digits is set to 16. If the
exponent X of the 'e' style conversion result is:
+
+ * If 16 > X >= -4, then the result uses decimal notation
+
+ * Otherwise, uses scientific notation with a maximum of 15 significant
digits after the decimal point
+
+ * Removes trailing zeros after the decimal point
+
+ * If there are no digits after the decimal point, removes the decimal point
+
+Example:
+
+| double | string | comment
|
+| -------------------------------- | ----------------------- |
----------------------------------------------------- |
+| 1234567890123456.12345 | "1234567890123456" | e < 16, does
not use scientific notation; 16 significant digits |
+| 12345678901234567.12345 | "1.234567890123457e+16" | e >= 16, uses
scientific notation; 16 significant digits |
+| 0.0001234567890123456789 | "0.0001234567890123457" | e >= -4, does
not use scientific notation; 16 significant digits |
+| 0.000000000000001234567890123456 | "1.234567890123456e-15" | e < -4, uses
scientific notation; 16 significant digits |
+| 123.456000 | "123.456" | Remove trailing
zeros |
+| 123.000 | "123" | Remove trailing
decimal point |
+| 0.0 | "0" |
|
+| -0.0 | "-0" | Negative zero
|
+| NaN | "NaN" |
|
+| Infinity | "Infinity" |
|
+| -Infinity | "-Infinity" |
|
+
+## Decimal
+
+Converts according to the decimal format of the numeric value. Non-negative
numbers have no '+' prefix, negative numbers have '-' prefix, without prefix 0.
+
+For Decimal(P\[,S]) type, when outputting, always displays S digits after the
decimal point. If the number of decimal places is less than S, it is padded
with zeros. For example, the number 123.456 of type Decimal(18, 6) is converted
to 123.456000.
+
+Example:
+
+```sql
+select cast(cast("123.456" as decimal(18, 6)) as string) as str_value;
++------------+
+| str_value |
++------------+
+| 123.456000 |
++------------+
+
+select cast(cast("-2147483648" as decimalv3(12, 2)) as string) as str_value;
++----------------+
+| str_value |
++----------------+
+| -2147483648.00 |
++----------------+
+```
+
+## Date
+
+Date type output format is "yyyy-MM-dd", which is 4-digit year, 2-digit month,
2-digit day, separated by "-".
+
+Example:
+
+```sql
+select cast(date('20210304') as string);
++----------------------------------+
+| cast(date('20210304') as string) |
++----------------------------------+
+| 2021-03-04 |
++----------------------------------+
+```
+
+## Datetime
+
+Datetime type output format is "yyyy-MM-dd HH:mm:ss\[.SSSSSS]". If the type's
`Scale` is not 0, then outputs the decimal point and `Scale` digits of
fractional seconds. Example:
+
+```sql
+select cast(cast('20210304' as datetime) as string);
++----------------------------------------------+
+| cast(cast('20210304' as datetime) as string) |
++----------------------------------------------+
+| 2021-03-04 00:00:00 |
++----------------------------------------------+
+
+select cast(cast('20020304121212.123' as datetime(3)) as string);
++-----------------------------------------------------------+
+| cast(cast('20020304121212.123' as datetime(3)) as string) |
++-----------------------------------------------------------+
+| 2002-03-04 12:12:12.123 |
++-----------------------------------------------------------+
+```
+
+## Time
+
+Time type is output in "hour:minute:second" format. The hour can be at most 3
digits, at least 2 digits, and can be negative; minutes and seconds are always
2 digits. If the type's `Scale` is not 0, then outputs the decimal point and
`Scale` digits of fractional seconds.
+
+Example:
+
+```sql
+select cast(cast('0' as time) as string);
++-----------------------------------+
+| cast(cast('0' as time) as string) |
++-----------------------------------+
+| 00:00:00 |
++-----------------------------------+
+
+select cast(cast('2001314' as time(3)) as string);
++--------------------------------------------+
+| cast(cast('2001314' as time(3)) as string) |
++--------------------------------------------+
+| 200:13:14.000 |
++--------------------------------------------+
+
+select cast(cast('-2001314.123' as time(3)) as string);
++-------------------------------------------------+
+| cast(cast('-2001314.123' as time(3)) as string) |
++-------------------------------------------------+
+| -200:13:14.123 |
++-------------------------------------------------+
+```
+
+## Array
+
+1. The string representation of an array starts with a left square bracket `[`
and ends with a right square bracket `]`.
+
+2. An empty array is represented as `[]`.
+
+3. Array elements in the string are separated by a comma followed by a space
`", "`.
+
+4. If an element in the array is of string type, its string representation is
surrounded by single quotes `'`.
+
+5. Non-string type elements are directly converted to their own string
representation without adding extra quotes.
+
+6. If an array element is `NULL`, it is represented as the string `null`.
+
+```sql
+mysql> select cast(array(1,2,3,4) as string);
++--------------------------------+
+| cast(array(1,2,3,4) as string) |
++--------------------------------+
+| [1, 2, 3, 4] |
++--------------------------------+
+```
+
+## Map
+
+1. The string representation of a Map starts with a left curly brace `{` and
ends with a right curly brace `}`.
+
+2. If the Map is empty, its string representation is `{}`.
+
+3. Key-value pairs in the Map are separated by a comma followed by a space `",
"` in the string.
+
+4. Key representation:
+
+ * If the key is of string type, its string representation is surrounded by
double quotes `"`.
+
+ * If the key is `NULL`, it is represented as the string `null`.
+
+ * For non-string type keys, they are directly converted to their own string
representation without adding extra quotes.
+
+5. Value representation:
+
+ * If the value is of string type, its string representation is surrounded
by double quotes `"`.
+
+ * If the value is `NULL`, it is represented as the string `null`.
+
+ * For non-string type values, they are directly converted to their own
string representation without adding extra quotes.
+
+6. Key-value pair structure: Each key-value pair is represented in the form
`key:value`, with the key and value separated by a colon `:`.
+
+```sql
+mysql> select cast(map("abc",123,"def",456) as string);
++------------------------------------------+
+| cast(map("abc",123,"def",456) as string) |
++------------------------------------------+
+| {"abc":123, "def":456} |
++------------------------------------------+
+```
+
+## Struct
+
+1. The string representation of a Struct starts with a left curly brace `{`
and ends with a right curly brace `}`.
+
+2. If the Struct is empty, its string representation is `{}`.
+
+3. The string representation of a Struct only displays values, not field names.
+
+4. Value representation:
+
+ * If the value is of string type, its string representation is surrounded
by double quotes `"`.
+
+ * If the value is `NULL`, it is represented as the string `null`.
+
+ * For non-string type values, they are directly converted to their own
string representation without adding extra quotes.
+
+5. Each value is separated by a comma followed by a space `", "`.
+
+```sql
+mysql> select struct(123,"abc",3.14);
++-----------------------------------------+
+| struct(123,"abc",3.14) |
++-----------------------------------------+
+| {"col1":123, "col2":"abc", "col3":3.14} |
++-----------------------------------------+
+1 row in set (0.03 sec)
+
+mysql> select cast(struct(123,"abc",3.14) as string);
++----------------------------------------+
+| cast(struct(123,"abc",3.14) as string) |
++----------------------------------------+
+| {123, "abc", 3.14} |
++----------------------------------------+
+```
diff --git
a/i18n/zh-CN/docusaurus-plugin-content-docs/current/sql-manual/basic-element/sql-data-types/conversion/cast-to-string.md
b/i18n/zh-CN/docusaurus-plugin-content-docs/current/sql-manual/basic-element/sql-data-types/conversion/cast-to-string.md
new file mode 100644
index 00000000000..bb9c7531162
--- /dev/null
+++
b/i18n/zh-CN/docusaurus-plugin-content-docs/current/sql-manual/basic-element/sql-data-types/conversion/cast-to-string.md
@@ -0,0 +1,329 @@
+---
+{
+ "title": "转换为字符串（输出）",
+ "language": "zh-CN"
+}
+---
+
+## Boolean
+
+如果为真值，返回1。否则返回0
+
+```sql
+mysql> select cast(true as string) , cast(false as string);
++----------------------+-----------------------+
+| cast(true as string) | cast(false as string) |
++----------------------+-----------------------+
+| 1 | 0 |
++----------------------+-----------------------+
+```
+
+## Integer
+
+按数值的十进制格式进行转换，不加前缀0，非负数不加前缀'+'号，负数加前缀'-'号。
+
+示例：
+
+```sql
+select cast(cast("123" as int) as string) as str_value;
++-----------+
+| str_value |
++-----------+
+| 123 |
++-----------+
+
+select cast(cast("-2147483648" as int) as string) as str_value;
++-------------+
+| str_value |
++-------------+
+| -2147483648 |
++-------------+
+```
+
+## Float
+
+将 float 值转换为字符串的详细规则：
+
+1. **特殊值处理**：
+
+ * `NaN`（非数字）转换为字符串 "NaN"
+
+ * `Infinity` 转换为字符串 "Infinity"
+
+ * `-Infinity` 转换为字符串 "-Infinity"
+
+2. **符号处理**：
+
+ * 负数添加 '-' 前缀
+
+ * 正数不添加符号前缀
+
+ * 零值特殊处理：
+
+ * `-0.0` 转换为 "-0"
+
+ * `+0.0` 转换为 "0"
+
+3. **格式规则**：
+
+ * 使用C printf 'g'
格式说明符语义（参考https://en.cppreference.com/w/c/io/fprintf），将浮点数转换为十进制或科学记数法，具体取决于数值和有效数字位数。有效数字位数设置为7，
如果采用'e'风格转换结果的指数为X，则：
+
+ * 如果7 > X >= -4，则结果使用十进制表示法
+
+ * 否则，使用科学计数法，小数点后最多保留6位有效数字
+
+ * 删除小数点后的后缀零
+
+ * 如果小数点后没有数字，则删除小数点
+
+示例：
+
+| float | string | comment |
+| -------------- | --------------- | --------------------- |
+| 123.456 | "123.456" | |
+| 1234567 | "1234567" | |
+| 123456.12345 | "123456.1" | e < 7，使用科学计数法，7位有效数字 |
+| 12345678.12345 | "1.234568e+07" | e >= 7，使用科学计数法，7位有效数字 |
+| 0.0001234567 | "0.0001234567" | e >= -4，不使用科学计数法 |
+| -0.0001234567 | "-0.0001234567" | e >= -4，不使用科学计数法 |
+| 0.00001234567 | "1.234567e-05" | e < -4，使用科学计数法 |
+| 123.456000 | "123.456" | Remove trailing zeros |
+| 123.000 | "123" | Remove decimal point |
+| 0.0 | "0" | |
+| -0.0 | "-0" | Negative zero |
+| NaN | "NaN" | |
+| Infinity | "Infinity" | |
+| -Infinity | "-Infinity" | |
+
+## Double
+
+将 double 值转换为字符串的详细规则：
+
+1. **特殊值处理**：
+
+ * `NaN`（非数字）转换为字符串 "NaN"
+
+ * `Infinity` 转换为字符串 "Infinity"
+
+ * `-Infinity` 转换为字符串 "-Infinity"
+
+2. **符号处理**：
+
+ * 负数添加 '-' 前缀
+
+ * 正数不添加符号前缀
+
+ * 零值特殊处理：
+
+ * `-0.0` 转换为 "-0"
+
+ * `+0.0` 转换为 "0"
+
+3. **格式规则**：
+
+ * 使用C printf 'g'
格式说明符语义（参考https://en.cppreference.com/w/c/io/fprintf），将浮点数转换为十进制或科学记数法，具体取决于数值和有效数字位数。有效数字位数设置为16，
如果采用'e'风格转换结果的指数为X，则：
+
+ * 如果16 > X >= -4，则结果使用十进制表示法
+
+ * 否则，使用科学计数法，小数点后最多保留15位有效数字
+
+ * 删除小数点后的后缀零
+
+ * 如果小数点后没有数字，则删除小数点
+
+示例：
+
+| double | string | comment
|
+| -------------------------------- | ----------------------- |
----------------------------- |
+| 1234567890123456.12345 | "1234567890123456" | e <
16，不使用科学计数法；16位有效数字 |
+| 12345678901234567.12345 | "1.234567890123457e+16" | e >=
16，使用科学计数法；16位有效数字 |
+| 0.0001234567890123456789 | "0.0001234567890123457" | e >=
-4，不使用科学计数法；16位有效数字 |
+| 0.000000000000001234567890123456 | "1.234567890123456e-15" | e <
-4，使用科学计数法；16位有效数字 |
+| 123.456000 | "123.456" | Remove trailing
zeros |
+| 123.000 | "123" | Remove trailing
decimal point |
+| 0.0 | "0" |
|
+| -0.0 | "-0" | Negative zero
|
+| NaN | "NaN" |
|
+| Infinity | "Infinity" |
|
+| -Infinity | "-Infinity" |
|
+
+## Decimal
+
+按数值的十进制格式进行转换，非负数不加前缀'+'号，负数加前缀'-'号，不加前缀0。
+
+对于Decimal(P\[,S])类型，在输出时，小数点后总是显示S位数字，小数位数不足S位时，后缀用0补齐。比如类型Decimal(18,
6)的数字123.456，会转换成123.456000。
+
+示例:
+
+```sql
+select cast(cast("123.456" as decimal(18, 6)) as string) as str_value;
++------------+
+| str_value |
++------------+
+| 123.456000 |
++------------+
+
+select cast(cast("-2147483648" as decimalv3(12, 2)) as string) as str_value;
++----------------+
+| str_value |
++----------------+
+| -2147483648.00 |
++----------------+
+```
+
+## Date
+
+Date 类型输出格式为 “yyyy-MM-dd”，即 4 位年，2 位月，2 位日，以 “-” 分隔。
+
+示例如下：
+
+```sql
+select cast(date('20210304') as string);
++----------------------------------+
+| cast(date('20210304') as string) |
++----------------------------------+
+| 2021-03-04 |
++----------------------------------+
+```
+
+## Datetime
+
+Datetime 类型输出格式为 “yyyy-MM-dd HH:mm:ss\[.SSSSSS]”，如果类型的 `Scale` 不为 0，则输出小数点及
`Scale` 位小数。示例如下：
+
+```sql
+select cast(cast('20210304' as datetime) as string);
++----------------------------------------------+
+| cast(cast('20210304' as datetime) as string) |
++----------------------------------------------+
+| 2021-03-04 00:00:00 |
++----------------------------------------------+
+
+select cast(cast('20020304121212.123' as datetime(3)) as string);
++-----------------------------------------------------------+
+| cast(cast('20020304121212.123' as datetime(3)) as string) |
++-----------------------------------------------------------+
+| 2002-03-04 12:12:12.123 |
++-----------------------------------------------------------+
+```
+
+## Time
+
+Time 类型按照“时:分:秒”格式输出。其中小时最多 3 位，最少 2 位，且可能为负数；分钟和秒都固定为 2 位。如果类型的 `Scale` 不为
0，则输出小数点及 `Scale` 位小数。
+
+示例如下：
+
+```sql
+select cast(cast('0' as time) as string);
++-----------------------------------+
+| cast(cast('0' as time) as string) |
++-----------------------------------+
+| 00:00:00 |
++-----------------------------------+
+
+select cast(cast('2001314' as time(3)) as string);
++--------------------------------------------+
+| cast(cast('2001314' as time(3)) as string) |
++--------------------------------------------+
+| 200:13:14.000 |
++--------------------------------------------+
+
+select cast(cast('-2001314.123' as time(3)) as string);
++-------------------------------------------------+
+| cast(cast('-2001314.123' as time(3)) as string) |
++-------------------------------------------------+
+| -200:13:14.123 |
++-------------------------------------------------+
+```
+
+## Array
+
+1. 数组的字符串表示以左方括号 `[` 开始，并以右方括号 `]` 结束。
+
+2. 空数组会为 `[]`。
+
+3. 数组元素在字符串中通过逗号加一个空格 `", "` 进行分隔。
+
+4. 如果数组中的元素是字符串类型，其字符串表示会被单引号 `'` 包围。
+
+5. 非字符串类型的元素会直接转换为其自身的字符串表示，不添加额外的引号。
+
+6. 数组元素为 `NULL`，其表示为字符串 `null`。
+
+```sql
+mysql> select cast(array(1,2,3,4) as string);
++--------------------------------+
+| cast(array(1,2,3,4) as string) |
++--------------------------------+
+| [1, 2, 3, 4] |
++--------------------------------+
+```
+
+## Map
+
+1. Map 的字符串表示以左花括号 `{` 开始，并以右花括号 `}` 结束。
+
+2. 如果 Map 为空，其字符串表示为 `{}`。
+
+3. Map 中的键值对在字符串中通过逗号加一个空格 `", "` 进行分隔。
+
+4. 键的表示:
+
+ * 如果键为字符串类型，则其字符串表示会被双引号 `"` 包围。
+
+ * 如果键为 `NULL`，其表示为字符串 `null`。
+
+ * 对于非字符串类型的键，直接转换为其自身的字符串表示，不添加额外的引号。
+
+5. 值的表示:
+
+ * 如果值为字符串类型，则其字符串表示会被双引号 `"` 包围。
+
+ * 如果值为 `NULL`，其表示为字符串 `null`。
+
+ * 对于非字符串类型的值，直接转换为其自身的字符串表示，不添加额外的引号。
+
+6. 键值对结构: 每个键值对的表示形式为 `key:value`，键和值之间用冒号 `:` 分隔。
+
+```sql
+mysql> select cast(map("abc",123,"def",456) as string);
++------------------------------------------+
+| cast(map("abc",123,"def",456) as string) |
++------------------------------------------+
+| {"abc":123, "def":456} |
++------------------------------------------+
+```
+
+## Struc
+
+1. Struct 的字符串表示以左花括号 `{` 开始，并以右花括号 `}` 结束。
+
+2. 如果 Struct 为空，其字符串表示为 `{}`。
+
+3. Struct 的字符串只会显示值，不会显示字段。
+
+4. 值的表示:
+
+ * 如果值为字符串类型，则其字符串表示会被双引号 `"` 包围。
+
+ * 如果值为 `NULL`，其表示为字符串 `null`。
+
+ * 对于非字符串类型的值，直接转换为其自身的字符串表示，不添加额外的引号。
+
+5. 每个值之间用逗号加一个空格 `", "` 分隔。
+
+```sql
+mysql> select struct(123,"abc",3.14);
++-----------------------------------------+
+| struct(123,"abc",3.14) |
++-----------------------------------------+
+| {"col1":123, "col2":"abc", "col3":3.14} |
++-----------------------------------------+
+1 row in set (0.03 sec)
+
+mysql> select cast(struct(123,"abc",3.14) as string);
++----------------------------------------+
+| cast(struct(123,"abc",3.14) as string) |
++----------------------------------------+
+| {123, "abc", 3.14} |
++----------------------------------------+
+```
diff --git a/sidebars.json b/sidebars.json
index 4879d5fa087..4503e315976 100644
--- a/sidebars.json
+++ b/sidebars.json
@@ -1109,6 +1109,7 @@
"items": [
"sql-manual/basic-element/sql-data-types/conversion/overview",
"sql-manual/basic-element/sql-data-types/conversion/cast-expr",
+
"sql-manual/basic-element/sql-data-types/conversion/cast-to-string",
"sql-manual/basic-element/sql-data-types/conversion/array-conversion",
"sql-manual/basic-element/sql-data-types/conversion/boolean-conversion",
"sql-manual/basic-element/sql-data-types/conversion/date-conversion",
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