To create a table in Oracle, you need to use the CREATE TABLE statement. Start by specifying the name of the table that you want to create, followed by a list of column names and their respective data types. You can also specify additional constraints such as NOT NULL, UNIQUE, PRIMARY KEY, FOREIGN KEY, and CHECK constraints. Once you have defined all the columns and constraints, you can execute the CREATE TABLE statement to create the table in the Oracle database. Remember to ensure that you have the necessary privileges to create tables in the database before executing the statement.
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How to enable table compression while creating a table in Oracle?
To enable table compression while creating a table in Oracle, you can use the COMPRESS option in the CREATE TABLE statement. Here is an example:
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CREATE TABLE demo_table ( id NUMBER, name VARCHAR2(50) ) COMPRESS FOR ALL OPERATIONS; |
In this example, the COMPRESS FOR ALL OPERATIONS clause enables table compression for all DML operations (insert, update, delete) on the demo_table table. You can also use COMPRESS FOR OLTP for OLTP workloads or COMPRESS BASIC for basic compression.
How to specify a column as NOT NULL while creating a table in Oracle?
When creating a table in Oracle, you can specify a column as NOT NULL by adding the constraint "NOT NULL" after the column definition. Here's an example of how to create a table with a column that is NOT NULL:
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CREATE TABLE example_table ( id NUMBER NOT NULL, name VARCHAR2(50) NOT NULL, age NUMBER ); |
In the above example, the columns "id" and "name" are specified as NOT NULL, which means that a value must be provided for these columns when inserting data into the table. If no value is provided, an error will occur. The "age" column does not have the NOT NULL constraint, so it can have NULL values.
How to specify data types for columns in an Oracle table?
In Oracle, you can specify the data types for columns in a table by including the data type in the column definition when creating the table. Here is an example of how to specify data types for columns in an Oracle table:
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CREATE TABLE table_name ( column1_name data_type(size), column2_name data_type(size), column3_name data_type(size), ... ); |
In the above example, replace table_name with the name of the table you want to create, column1_name, column2_name, column3_name, etc. with the names of the columns you want to include in the table, and data_type(size) with the specific data type and size (if applicable) for each column.
Here are some common data types that you can use in Oracle:
- NUMBER(size, precision): Numeric data type with a specified size and precision
- VARCHAR2(size): Variable-length character data with a specified maximum size
- DATE: Date data type
- CHAR(size): Fixed-length character data with a specified size
- CLOB: Character large object data type for storing large amounts of character data
- BLOB: Binary large object data type for storing large amounts of binary data
You can refer to the Oracle documentation for a full list of data types and their descriptions.
How to add an index to a column in an existing Oracle table?
To add an index to a column in an existing Oracle table, you can use the following SQL command:
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CREATE INDEX index_name ON table_name(column_name); |
Replace index_name with the name you want to give to the index, table_name with the name of the existing table, and column_name with the name of the column you want to index.
For example, if you have a table named employees and you want to add an index to the last_name column, you can use the following command:
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CREATE INDEX idx_last_name ON employees(last_name); |
