Sybase SQL Anywhere - STRING Function - Concatenate Strings

STRING function concatenates one or more strings into a single string.

Quick Example:

   -- Concatenate strings AB and CD
   SELECT STRING('AB', 'CD');
   -- Result: ABCD

STRING Function Overview

Summary information:

Syntax	STRING(string_expression, …)
Return Type	LONG VARCHAR
NULL Values	NULL value in a parameter is treated as '' (empty string)
	But STRING returns NULL if all parameters are NULL
Parameter Conversion	Number and datetime parameters are implicitly converted to string before concatenation
Single Parameter	STRING with one parameter can be used to convert an expression to string
Alternatives	\|\| operator	NULL is ''	Implicit casting
	+ operator	Result is NULL if any parameter is NULL	Explicit casting

Last Update: Sybase SQL Anywhere 12.0

STRING function concatenates one or more string expressions into a single string:

   SELECT STRING('A', 'B', 'C');
   -- Result: ABC

NULL value in any parameter is treated as '' (empty string):

   SELECT STRING('A', NULL, 'B');
   -- Result: AB

But if all parameters evaluate to NULL, STRING returns NULL, not empty string:

   SELECT STRING(NULL, NULL, NULL);
   -- Result: NULL

STRING function implicitly converts numbers and datetime values to string before concatenation:

   SELECT STRING(1, 2, 3);
   -- Result: 123

You can also use || and + operators to concatenate strings.

|| operator is equal to STRING function, it treats a NULL parameter as '' (empty string), and casts non-string expressions to string implicitly:

  SELECT 'A' || NULL || 'B';
  -- Result: AB
 
  SELECT 1 || 2 || 3;
  -- Result: 123

+ operator returns NULL if any expression is NULL, and it also requires explicit casting for non-string data types:

  SELECT 'A' + NULL + 'B';
  -- Result: NULL
 
  -- Arithmetic operation is performed without casting to string
  SELECT 1 + 2 + 3;
  -- Result: 6

String concatenation in other databases ( denotes differences):

Oracle:

CONCAT(string1, string2)	2 arguments only	NULL is '' (empty string)
\|\| Operator	NULL is ''

For more information, see Convert STRING to Oracle.

SQL Server:

+ Operator	If any value is NULL, the result is NULL, unless CONCAT_NULL_YIELDS_NULL is OFF
+= Operator	Transact-SQL only	s1 += s2 is equal to s1 = s1 + s2
\|\| Operator	Not available
CONCAT Function	Not available

MySQL:

\|\| Operator	Result is NULL if any value is NULL	sql_mode PIPES_AS_CONCAT or ANSI must be set
CONCAT(s1, s2, ...)	Result is NULL if any value is NULL
CONCAT_WS(sep, s1, s2, …)	NULL is ''	Allows to specify a separator
GROUP_CONCAT	NULL values skipped	Concatenates values within a group

PostgreSQL:

\|\| Operator	If any value is NULL, the result is NULL
CONCAT(s1, s2, …)	NULL is ''	Implicit Casting
CONCAT_WS(sep, s1, s2, …)	NULL is ''	Allows to specify a separator