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How to Create A Table In A Newly Created Database In Postgresql?

4 minutes read

To create a table in a newly created database in PostgreSQL, you first need to connect to the database using a tool like pgAdmin or the psql command line interface. Once connected, you can use the CREATE TABLE statement to define the columns and data types for your table. You can also specify constraints such as primary keys, foreign keys, and unique constraints during the table creation process. After defining the table structure, you can then insert data into the table using the INSERT INTO statement.


How to check the list of databases in postgresql?

To check the list of databases in PostgreSQL, you can use the following command:

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\l


Or you can also use the following SQL query:

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SELECT datname FROM pg_database;



How to modify a table in postgresql?

To modify a table in PostgreSQL, you can use the ALTER TABLE statement. Here are some common actions you can perform to modify a table:

  1. Add a new column:
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ALTER TABLE table_name
ADD column_name data_type;


  1. Rename a column:
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ALTER TABLE table_name
RENAME column_name TO new_column_name;


  1. Change the data type of a column:
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ALTER TABLE table_name
ALTER COLUMN column_name TYPE new_data_type;


  1. Add a constraint to a column:
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ALTER TABLE table_name
ADD CONSTRAINT constraint_name CHECK (column_name > value);


  1. Rename a table:
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ALTER TABLE old_table_name
RENAME TO new_table_name;


  1. Drop a column:
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ALTER TABLE table_name
DROP COLUMN column_name;


Remember to use caution when modifying a table as it can affect the existing data and relationships within the database. It's always a good idea to back up your data before making any significant modifications to a table.


What is the default port for postgresql?

The default port for PostgreSQL is 5432.


How to add a new column to a table in postgresql?

To add a new column to a table in PostgreSQL, you can use the ALTER TABLE statement with the ADD COLUMN clause. Here is an example of how to add a new column named new_column to a table named your_table:

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ALTER TABLE your_table
ADD COLUMN new_column datatype;


Replace your_table with the name of your table and new_column with the name of the new column you want to add. You also need to specify the data type of the new column after the datatype keyword.


For example, if you want to add a new column named email of type VARCHAR(255) to a table named users, you would use the following SQL statement:

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ALTER TABLE users
ADD COLUMN email VARCHAR(255);


Make sure to replace users with the name of your table and email with the name of the new column you want to add. The data type VARCHAR(255) specifies that the column will store variable-length character strings with a maximum length of 255 characters.


How to create a new table in postgresql?

To create a new table in PostgreSQL, you can use the following SQL command:

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CREATE TABLE table_name (
    column1 data_type1,
    column2 data_type2,
    column3 data_type3,
    ...
);


Here's an example of creating a table named "employees" with columns for employee ID, name, and salary:

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CREATE TABLE employees (
    employee_id SERIAL PRIMARY KEY,
    name VARCHAR(50),
    salary DECIMAL(10, 2)
);


This command will create a new table named "employees" with three columns: "employee_id" as a serial primary key, "name" as a VARCHAR data type with a maximum length of 50 characters, and "salary" as a DECIMAL data type with a precision of 10 digits and a scale of 2 decimal places.


After running the CREATE TABLE command, you can query the table structure to ensure that the table has been successfully created:

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SELECT column_name, data_type
FROM information_schema.columns
WHERE table_name = 'employees';



How to view the data in a table in postgresql?

To view the data in a table in PostgreSQL, you can use the following SQL query:

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SELECT * FROM table_name;


Replace table_name with the name of the table you want to view. This query will retrieve all the columns and rows from the specified table. You can also specify specific columns to display by replacing * with the column names separated by commas.


Alternatively, you can use a graphical user interface tool like pgAdmin or DBeaver to view the data in a table. Simply connect to your PostgreSQL database and navigate to the table you want to view, then right-click on it and select "View/Edit Data" or similar option. This will display the table data in a visual format.

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