Date and Time Built-in Functions

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  1. Date and Time Data Types: SQL provides data types for dates, times, and timestamps, with specific formats:

    • Date: YYYYMMDD
    • Time: HHMMSS
    • Timestamp: YYYYXXDDHHMMSSZZZZZZ (where XX represents the month and ZZZZZZ represents microseconds)

  2. Date and Time Functions: SQL offers functions to extract specific components from dates and times:

    • DAY(): Extracts the day portion from a date.
    • Other functions include MONTH(), YEAR(), DAYOFMONTH(), DAYOFWEEK(), DAYOFYEAR(), WEEK(), HOUR(), MINUTE(), SECOND().

  3. Using Date and Time Functions:

    • These functions can be used in SQL queries, particularly in the SELECT and WHERE clauses.
    • Example: SELECT DAY(RescueDate), RescueDate FROM PetRescue WHERE Animal = 'cat';

  4. Date Arithmetic:

    • SQL allows for arithmetic operations with dates and times.
    • Example: Calculating the date three days after each rescue date using DATE_ADD().
    • Example: Finding the number of days passed since each rescue date till now using CURRENT_DATE - RescueDate.

  5. Special Registers:

    • SQL provides special registers like CURRENT_DATE and CURRENT_TIME to retrieve the current date and time.
    • These registers can be used in calculations and comparisons with other dates and times.

Understanding these date and time functions and techniques allows SQL users to manipulate and analyze temporal data effectively, enabling tasks such as date extraction, arithmetic operations, and comparisons with current dates and times.

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