To work around this, you can use a synonym for the table in the stored procedure, and update the synonym definition if there is a change in the name or location of the table. Now, if the table name changes or the table is moved to some other location then your stored procedure will stop working. You can modify the synonym definition to accommodate any changes in the name or location of the underlying objects.įor example, suppose that you are using a table in one of your stored procedures. This ensures that you do not have to modify your SQL statements to perform operation on the object in different schemas.Ĭhanges in the underlying objects: The synonyms insulate you from any changes in the name or location of the underlying objects on which you are performing an operation. Whenever you need to perform operation on the “Prod.Employee” table, modify the definition of the “EMP” synonym to point it to the “Prod.Employee” table. To get around this issue, you can create a synonym for the “Test.Employee” table (say “EMP”), and then use it in your SQL statements. If you want to use the “Employee” table in the production schema, you must now use Prod.Employee or Employee (change the default schema to “Prod”) in your SQL statement. Thus, the applications based on the synonym continue to function without modification in the SQL statement.įor example, suppose you have two identical schemas for your test and production environments: “Test” and “Prod.” To access a table called “Employee” in the “Test” schema, you must use Test.Employee or Employee (if “Test” is the default schema) in your SQL statement. If you need to access the underlying object in a different schema, modify the definition of the synonym to point to the object in a different schema. ![]() You can create a synonym for an object in a schema, and use the synonym in your SQL statement to access the object. Working with different schemas: If you are working with different schemas, and need to access the objects across schemas, you have to use different SQL statements to access those objects. ![]() Synonyms are helpful in the following scenarios: For more information about synonyms in Oracle, see. ![]() A synonym is an alias or friendly name for the database objects (such as tables, views, stored procedures, functions, and packages). The following example retrieves half the rows based on quantity.The Oracle Database adapter allows you to perform operations on synonyms. The following example includes rows with ties. SELECT *įor the preceding example, the result looks as shown following. The following example retrieves the three most ordered items by quantity. ) INSERT INTO OrderItems (OrderID, Item, Quantity) The following example creates the OrderItems table. ![]() To replace the PERCENT option, first calculate how many rows the query returns and then calculate the fixed number of rows to be returned based on that number.īecause this technique introduces significant added complexity and three accesses to the source table, consider changing the logic to introduce a tie-breaker into the ORDER BY clause. It is automatically converted by the AWS Schema Conversion Tool (AWS SCT) except for the WITH TIES and PERCENT modifiers. You can use the LIMIT… OFFSET syntax to replace the functionality of TOP(n) and FETCH… OFFSET in SQL Server. If you use TOP (n) without WITH TIES and there are additional rows that have the same ordering value as the last row in the group of n rows, the query is also non-deterministic because the last row may be any of the rows that share the same ordering value. TOP (n) WITH TIES is used to allow overriding the n maximal number or percentage of rows specified in case there are additional rows with the same ordering values as the last row. When you use PERCENT, n can be any value from 1-100. TOP (n) PERCENT is used to designate a percentage of the rows to be returned instead of a fixed maximal row number limit (n).
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