This is as per documentation on Consideration when using create Table command, portion of the document says,
Identity Columns
Identity column support differs as follows:
- Sybase IQ supports IDENTITY or DEFAULT AUTOINCREMENT as a default value. Sybase IQ supports identity columns of any numeric type with any precision and scale 0, and the column can be NULL. Sybase IQ identity columns must be positive and are limited by the range of the data type. Sybase IQ supports a single identity column per table, and requires database option IDENTITY_INSERT set to a table name for explicit inserts and updates. To drop a table with an IDENTITY column, you cannot have IDENTITY_INSERT set to that table. The table can contain data when adding an identity column. Tables derived using SELECT INTO do not have Identity/Autoincrement columns. Sybase IQ views cannot contain IDENTITY/DEFAULTAUTOINCREMENT columns.
- SQL Anywhere supports the AUTOINCREMENT default value. SQL Anywhere supports identity columns of any numeric type with any allowable scale and precision. The identity column value can be positive, negative, or zero, limited by the range of the data type. SQL Anywhere supports any number of identity columns per table, and does not require identity_insert for explicit inserts, drops, and updates. The table must be empty when adding identity columns. SQL Anywhere identity columns can be altered to be nonidentity columns, and vice versa. You can add or drop AUTOINCREMENT columns from SQL Anywhere views.
- Adaptive Server Enterprise supports a single identity column per table. Adaptive Server Enterprise identity columns are restricted to only numeric data type scale 0, maximum precision 38. They must be positive, are limited by the range of the data type, and cannot be null. Adaptive Server Enterprise requires identity_insert for explicit inserts and drops, but not for updates to the identity column. The table can contain data when you add an identity column. Adaptive Server Enterprise users cannot explicitly set the next value chosen for an identity column. Adaptive Server Enterprise views cannot contain IDENTITY/AUTOINCREMENT columns. When using SELECT INTO under certain conditions, Adaptive Server Enterprise allows Identity/Autoincrement columns in the result table if they were in the table being selected from.