To select a random record with Oracle:

   SELECT first_name, last_name
     FROM customer
    ORDER BY dbms_random.value;

To select only one random record from Oracle database table:

   SELECT first_name, last_name
     FROM (SELECT first_name, last_name
             FROM customer
            ORDER BY dbms_random.value)
    WHERE ROWNUM = 1;

To limit the number of random records returned by SELECT statement in Oracle to 10:

   SELECT first_name, last_name
     FROM (SELECT first_name, last_name
             FROM customer
            ORDER BY dbms_random.value)
    WHERE ROWNUM < 10;

Solution
To find tablespace for tables in current user’s schema:

SELECT table_name, tablespace_name, STATUS
  FROM user_tables
 WHERE table_name LIKE :p_table_pattern;

To find tablespaces for tables from all schemas that current user can access:

SELECT table_name, tablespace_name, STATUS
  FROM all_tables
 WHERE table_name LIKE :p_table_pattern;

To find tablespaces for all tables from all schemas, you need to be granted SYSDBA system privilege:

SELECT table_name, tablespace_name, STATUS
  FROM dba_tables
 WHERE table_name LIKE :p_table_pattern;

Solution
The following SQL query returns information about a FIND_USER procedure, defined in the current user’s schema. The information returned includes procedure name, date procedure was created and date procedure was updated.

SELECT o.object_name AS object_name,
       o.created AS date_created,
       o.last_ddl_time AS date_updated
  FROM user_objects o
 WHERE o.object_type = 'PROCEDURE'
       AND o.object_name ='FIND_USER';

The following SQL query retrieves similar information for any PL/SQL procedure in any Oracle Database schema you have granted access to.

SELECT o.object_name AS object_name,
       o.owner AS object_schema,
       o.created AS date_created,
       o.last_ddl_time AS date_updated
  FROM all_objects o
 WHERE o.object_type = 'PROCEDURE'
       AND o.object_name ='FIND_USER';

Database Administrator can query information about procedures, defined in any schema.

SELECT o.object_name AS object_name,
       o.owner AS object_schema,
       o.created AS date_created,
       o.last_ddl_time AS date_updated
  FROM dba_objects o
 WHERE o.object_type = 'PROCEDURE'
       AND o.object_name ='FIND_USER';

See Also Find Invalid Objects in Oracle Databasea
Back to Oracle Database Tips.

Solution

SELECT o.object_name AS object_name,
       o.object_type AS object_type,
       o.owner AS object_schema
  FROM all_objects o
 WHERE o.STATUS = 'INVALID';

Database Administrators (DBA) can query DBA_OBJECTS data dictionary view.

SELECT o.object_name AS object_name,
       o.object_type AS object_type,
       o.owner AS object_schema
  FROM dba_objects o
 WHERE o.STATUS = 'INVALID';

See Also Find Invalid Objects in Oracle Databasea
Back to Oracle Database Tips.

     <name> [CONSTANT] <datatype> [NOT NULL] [:= | DEFAULT <expr>]

• <name> is the name of the variable or constant;
• <datatype> may be scalar, composite datatype, reference or LOB;
• <expr> is a literal value, another variable or any PL/SQL expression. The result of the expression is used to assign the default value of the variable or constant.

• If you are defining a constant, you must provide the value of the constant in the definition.
• TABLE, RECORD, NESTED TABLE and VARRAY are composite types.
• To define scalar type you can refer to [schema.]object%TYPE or cursor%TYPE.
• For record type you can refer to [schema.]object%ROWTYPE.

Examples:

DECLARE
  --Define some scalar variables
  v_year NUMBER(4);
  v_pin VARCHAR2(12);
  v_min_amount NUMBER(20, 2) := 25000;
 
  --Define a record type
  TYPE t_customer IS RECORD (
    id NUMBER(18),
    first_name VARCHAR2(32),
    last_name VARCHAR2(32),
  );
  --Declare a record variable
  v_customer t_customer;
 
  --Declare a composite type to hold a list of records
  TYPE t_customer_list IS TABLE OF t_customer;
 
  --Declare a record variable refering an existing table
  v_employee employee%ROWTYPE;
BEGIN
   v_year := 2010;
   -- More PL/SQL code here.
END;

Declare RECORD variables and types

A specific RECORD TYPE corresponding to a fixed number (and datatype) of underlying table columns can simplify the job of defining variables.

%TYPE is used to declare a field with the same type as that of a specified table’s column.
%ROWTYPE is used to declare a record with the same types as found in the specified database table, view or cursor.

Declare RECORD type

TYPE <type_name> IS RECORD(
    <field_declaration>,...);

Each record field is declared with its ‘field_declaration’:

   <field_name> {<field_type> |
               <variable>%TYPE |
               <table.column>%TYPE |
               <table>%ROWTYPE}
               [ [NOT NULL] {:= | DEFAULT} <expr> ]

The <field_type> can be any PL/SQL data type except REF CURSOR.

To declare a record variable:

   <variable_identifier> <type_name>;

You can declare a variable based on a record reference using %ROWTYPE:

   <variable_name> <table_or_curosr_name>%ROWTYPE

The number of variables and their data type is evaluated at run-time.

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Create a Oracle Database Table with calculated virtual column:

CREATE TABLE customer(
   first_name VARCHAR2(32),
   last_name VARCHAR2(32),
   full_name AS (first_name || ' ' || last_name)
);

Add a new calculated virtual column to an existing Oracle Database Table:

ALTER TABLE customer
          ADD full_name AS (first_name || ' ' || last_name)

Some of the virtual column benefits include:

• Automatic re-computation of derived columns for ad-hoc query tools.
• Reduction in redundant disk space for columns that must be derived from other columns (e.g. a MONTH column that is derived from another DATE column).
• Keep business logic in a single place.
• Easier interval partitioning based on calculated columns.

You should keep in mind that:

• virtual columns may not reference other virtual columns;
• virtual columns only within the containing table. You cannot reference columns within other tables.

Oracle Database virtual columns has the nice side effect of assisting in streamlining partitioning. For example, assume that we have a table that is partitioned by year-month (i.e. 2007-07). With 11g virtual columns, instead of creating separate column, we can simply compute the partition key virtually, using a DATE column.

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SELECT first_name || CHR(9) || last_name
  FROM employee;

You can use this approach to add other special characters to Oracle query.

Back to Oracle Database Tips
.

DECLARE
  t_cursor IS REF CURSOR;
  my_cursor t_cursor;
  v_customer RECORD (
     customer_id NUMBER(18),
	 amount NUMBER(22, 2)
  );
BEGIN
  OPEN my_cursor FOR SELECT customer_id, 
                            amount 
                       FROM monthly_sales;
  LOOP
    FETCH my_cursor INTO v_customer;
	EXIT WHEN my_cursor%NOTFOUND;
 
	dbms_output.put_line(v_customer.amount);
  END LOOP;
END;

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-- Create a new table with distinct row values.
CREATE TABLE temp_table_name AS
   SELECT DISTINCT * 
      FROM source_table_name;
 
-- Replace the original table with the new table.
DROP TABLE source_table_name;
RENAME temp_table_name TO source_table_name;

Of course in real life the are always complications. For example, the above example doesn’t take in account constraints and indexes. You should carefully investigate all dependencies to avoid performance degradation and to preserve data integrity.