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

Summary information:

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

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