There also exist algebraic operators (+,  -, *, /) to perform string concatenation and deletion.

SELECT "Hello"+"World" FROM Stream
=> "HelloWorld"
SELECT "HelloWorld"-"World" FROM Stream
=> "Hello"
SELECT "HelloWorld"*3 FROM Stream
=> "HelloWorldHelloWorldHelloWorld"
SELECT "HelloWorldHelloWorldHelloWorld"/"World" FROM Stream
=> 3

Concat(String, String)

Returns a new string that is a concatenating the arguments.

SubString(String, Number, Number)

Returns a new string that is a substring of the value with given begin and end index

SELECT substring("Hello World",1,3) FROM Stream
=> "el"

Length(String)

Returns the length of a string.

SELECT length("Hello") FROM Stream
=> 5

Upper(String)

Returns the string converted to uppercase.
 

SELECT upper("Hello World") FROM Stream
=> "HELLO WORLD"

Lower(String)

Returns the string converted to lowercase.

SELECT lower("Hello World") FROM Stream
=> "hello world"