This function is used to return a string concatenated from multiple input strings that are separated by specified separators.

concat_ws(string <separator>, string <str1>, string <str2>[,...])

concat_ws(string <separator>, array<string> <a>)

Returns the result of joining all the strings in the parameters or the elements in an array using a specified separator.

**Table 1** Parameters
Parameter	Mandatory	Type	Description
separator	Yes	STRING	Separator of the STRING type
str1, str2	Yes	STRING	At least two strings must be specified. The value is of the STRING type. If the value is of the BIGINT, DECIMAL, DOUBLE, or DATETIME type, the value is implicitly converted to the STRING type for calculation.
a	Yes	ARRAY	The elements in an array are of the STRING type.

The return value is of the STRING or STRUCT type.

If the value of str1 or str2 is not of the STRING, BIGINT, DECIMAL, DOUBLE, or DATETIME type, an error is reported.
If the value of the parameter (string to be concatenated) is NULL, the parameter is ignored.
If there is no input parameter (string to be concatenated), NULL is returned.

Use a colon (:) to connect strings ABC and DEF. An example command is as follows:
The value ABC:DEF is returned.
```
select concat_ws(':','ABC','DEF');
```
The value of any input parameter is NULL. An example command is as follows:
The value avg:18 is returned.
```
select concat_ws(':','avg',null,'18');
```
Use colons (:) to connect elements in the array ('name', 'lilei'). An example command is as follows:
The value name:lilei is returned.
```
select concat_ws(':',array('name', 'lilei'));
```