Add MAKE_SET() and LTRIM() examples (#16954) (#17313)

functions-and-operators/string-functions.md

@@ -1238,11 +1238,135 @@ SELECT LPAD('TiDB',-2,'>');
 
 ### [`LTRIM()`](https://dev.mysql.com/doc/refman/8.0/en/string-functions.html#function_ltrim)
 
-Remove leading spaces.
+The `LTRIM()` function removes leading spaces from a given string.
+
+If the argument is `NULL`, this function returns `NULL`.
+
+> **Note:**
+>
+> This function only removes the space character (U+0020) and does not remove other space-like characters such as tab (U+0009) or non-breaking space (U+00A0).
+
+Examples:
+
+In the following example, the `LTRIM()` function removes the leading spaces from `'    hello'` and returns `hello`.
+
+```sql
+SELECT LTRIM('    hello');
+```
+
+```
++--------------------+
+| LTRIM('    hello') |
++--------------------+
+| hello              |
++--------------------+
+1 row in set (0.00 sec)
+```
+
+In the following example, [`CONCAT()`](#concat) is used to enclose the result of `LTRIM('    hello')` with `«` and `»`. This formatting makes it a bit easier to see that all leading spaces are removed.
+
+```sql
+SELECT CONCAT('«',LTRIM('    hello'),'»');
+```
+
+```
++------------------------------------+
+| CONCAT('«',LTRIM('    hello'),'»') |
++------------------------------------+
+| «hello»                            |
++------------------------------------+
+1 row in set (0.00 sec)
+```
 
 ### [`MAKE_SET()`](https://dev.mysql.com/doc/refman/8.0/en/string-functions.html#function_make-set)
 
-Return a set of comma-separated strings that have the corresponding bit in bits set.
+The `MAKE_SET()` function returns a set of comma-separated strings based on whether a corresponding bit in the `bits` argument is set to `1`.
+
+Syntax:
+
+```sql
+MAKE_SET(bits, str1, str2, ...)
+```
+
+- `bits`: controls which subsequent string arguments to include in the result set. If `bits` is set to `NULL`, the function returns `NULL`.
+- `str1, str2, ...`: a list of strings. Each string corresponds to a bit in the `bits` argument from right to left. `str1` corresponds to the first bit from the right, `str2` corresponds to the second bit from the right, and so on. If the corresponding bit is `1`, the string is included in the result; otherwise, it is not included.
+
+Examples:
+
+In the following example, because all bits are set to `0` in the `bits` argument, the function does not include any subsequent strings in the result and returns an empty string.
+
+```sql
+SELECT MAKE_SET(b'000','foo','bar','baz');
+```
+
+```
++------------------------------------+
+| MAKE_SET(b'000','foo','bar','baz') |
++------------------------------------+
+|                                    |
++------------------------------------+
+1 row in set (0.00 sec)
+```
+
+In the following example, because only the first bit from the right is `1`, the function only returns the first string `foo`.
+
+```sql
+SELECT MAKE_SET(b'001','foo','bar','baz');
+```
+
+```
++------------------------------------+
+| MAKE_SET(b'001','foo','bar','baz') |
++------------------------------------+
+| foo                                |
++------------------------------------+
+1 row in set (0.00 sec)
+```
+
+In the following example, because only the second bit from the right is `1`, the function only returns the second string `bar`.
+
+```sql
+SELECT MAKE_SET(b'010','foo','bar','baz');
+```
+
+```
++------------------------------------+
+| MAKE_SET(b'010','foo','bar','baz') |
++------------------------------------+
+| bar                                |
++------------------------------------+
+1 row in set (0.00 sec)
+```
+
+In the following example, because only the third bit from the right is `1`, the function only returns the third string `baz`.
+
+```sql
+SELECT MAKE_SET(b'100','foo','bar','baz');
+```
+
+```
++------------------------------------+
+| MAKE_SET(b'100','foo','bar','baz') |
++------------------------------------+
+| baz                                |
++------------------------------------+
+1 row in set (0.00 sec)
+```
+
+In the following example, because all bits are `1`, the function returns all three strings in a comma-separated result set.
+
+```sql
+SELECT MAKE_SET(b'111','foo','bar','baz');
+```
+
+```
++------------------------------------+
+| MAKE_SET(b'111','foo','bar','baz') |
++------------------------------------+
+| foo,bar,baz                        |
++------------------------------------+
+1 row in set (0.0002 sec)
+```
 
 ### [`MID()`](https://dev.mysql.com/doc/refman/8.0/en/string-functions.html#function_mid)