In the world of databases and data manipulation, timestamps are quintessential. They provide an accurate record of the data creation or modification in the database. In SQL, it is often necessary to set a default timestamp value to be the current timestamp. This becomes particularly useful in instances where we need to track the time a particular event occurred or in any case, where default time is required. This article will shed light on this aspect of SQL programming.
SQL, an abbreviation for Structured Query Language, is a standard language for managing and manipulating databases. It has several built-in functions and libraries that aid in efficient database handling and one such feature is the ability to set the default timestamp value to the current timestamp.
Creating a SQL Table with a Default Timestamp Value
Creating a SQL table with a default timestamp requires utilization of the DEFAULT expression, which can be used to insert the current timestamp in a column if no specific value is provided during the table creation.
CREATE TABLE Employees (
ID int,
Name varchar(255),
JoiningDate timestamp DEFAULT CURRENT_TIMESTAMP
);
The code above creates a table named Employees. Notice the `JoiningDate` column which has been set to use the `CURRENT_TIMESTAMP` as the default value.
Explanation of the Code
Let’s break down the code to understand how it works.
- The `CREATE TABLE` statement initializes the creation of a new table.
- The `Employees` is the name assigned to the table.
- We declare the `ID` and `Name` columns in the table with respective data types.
- The `JoiningDate` column is assigned with `timestamp` data type and DEFAULT CURRENT_TIMESTAMP expression which will automatically assign the current timestamp each time a new record is created.
Upon creation of a new employee record without specifying the `JoiningDate`, the SQL server will use the current timestamp as the default value.
INSERT INTO Employees (ID, Name) VALUES (1, 'John Doe');
In the above code snippet, only `ID` and `Name` are being inserted into the Employees table. `JoiningDate` is left out, and as a result, SQL server inserts the current timestamp.
SQL Libraries and Functions involved
In SQL, several built-in libraries and functions pave the way for efficient and straightforward database handling. The `DEFAULT` keyword sets a default value for a column when no value is specified.
The `CURRENT_TIMESTAMP` is a function which returns the current date and time. When paired with `DEFAULT`, it automatically sets the current date and time whenever a new record is created, and no explicit value is set for that column.
With appropriate SQL knowledge, setting a default timestamp value to be the current timestamp is a breeze and can considerably enhance the efficiency of managing databases.
