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Working with tables
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Altering tables in
Sybase Central
The property sheets for tables and columns display all the table or column
attributes. You can alter a table definition in Sybase Central by displaying the
property sheet for the table or column you wish to change, altering the property,
and clicking OK to commit the change.
Altering tables in a
join index
You cannot ADD, DROP or MODIFY a base table column that participates in a
join condition of a join index. To alter joined columns, you must first drop the
join index, alter the table, and then recreate the join index. See “Using join
indexes” for complete information on join indexes.
Dropping tables
The following DROP TABLE statement deletes all the records in the skill table
and then removes the definition of the
skill table from the database
DROP TABLE skill
Like the CREATE statement, the DROP statement automatically executes a
COMMIT before and after dropping the table. This makes permanent all
changes to the database since the last
COMMIT or ROLLBACK.
The
DROP statement also drops all indexes on the table, except if any column
in the table participates in a join index.
If you only want to remove data rows but not the table itself, use the
TRUNCATE TABLE statement. If you truncate a table while other users are
reading from it, the normal rules of table versioning apply, that is, old table
versions remain until readers' transactions complete; see Chapter 8,
“Transactions and Versioning” for details.
DROP TABLE and TRUNCATE TABLE are very fast, taking only seconds to
occur. The size of the data does not effect the speed of the operation.
For a full description of the
DROP statement, see Adaptive Server IQ Reference
Manual.
❖ To drop a table in Sybase Central:
1 Connect to the database.
2 Click the Tables folder for that database.
3 Right-click the table you wish to delete, and select Delete from the pop-up
menu.