PostgreSQL

LIMIT is an optional clause in PostgreSQL that is executed with a SELECT query to fetch only specific/limited records from a table.

“DELETE CASCADE” feature in Postgres ensures referential integrity by automatically deleting all child records when the corresponding parent record is deleted.

The NOW() function returns the current date and time along with the time zone information. The returned data type of this function is “TIMESTAMPTZ”.

To find the database and table sizes in PostgreSQL, the pg_database_size() and the pg_relation_size() functions are used, respectively.

To describe tables in PostgreSQL, the “\dt”, “\dt+” or the “\d tab_name” meta-commands and “information_schema” are used.

In PostgreSQL, the length of the string can be found by using functions like LENGTH(), OCTET_LENGTH(), and BIT_LENGTH().

To create a DATE type column, specify the column’s name followed by the DATE keyword. By default, the DATE data type stores data in “YYYY-MM-DD” format.

To update the table values/data in PostgreSQL, the UPDATE command is used. This statement allows the user to update the previous data to new data values.

In PostgreSQL, the SELECT statement is used with the FROM clause to get/fetch the required result from the specified table.

To rename a table in PostgreSQL, use the ALTER TABLE statement along with the RENAME TO clause. A table can be renamed manually using pgAdmin.

To insert values/rows into a Postgres table, use the INSERT INTO statement. The VALUE clause is used to specify the values that need to be inserted.

In Postgres, a Primary key can be added to a column during table creation. It can be added to an existing table using the ALTER TABLE ADD CONSTRAINT command.

In PostgreSQL, the DELETE statement is used with the FROM clause to delete a single, multiple, or all rows of a specific table.

To create a table in PostgreSQL, execute the CREATE TABLE statement either in pgAdmin or in psql. Postgres tables can also be created manually using pgAdmin.

To create a database in PostgreSQL, execute the “CREATE DATABASE” command in the SQL Shell or pgAdmin. Users can also create databases manually using pgAdmin

To drop/delete a column from a PostgreSQL table, we can use the ALTER TABLE statement and the DROP COLUMN clause together.

Execute the DROP TABLE command either in SQL Shell or in pgAdmin to drop a particular table in Postgres. A table can also be dropped manually using pgAdmin.

To switch a database in Postgres, execute the “\c db_name” or “\connect db_name” command in psql. Or you can switch a database manually using pgAdmin.