SQL - Date Functions Complete Reference
Date and time handling sits at the core of nearly every production database. Orders have timestamps. Users have birthdates. Subscriptions expire. Reports filter by date ranges. Get date functions…
Read more →Date
SQL - DATE_TRUNC() - Truncate Date
Date truncation is the process of rounding a timestamp down to a specified level of precision. When you truncate 2024-03-15 14:32:45 to the month level, you get 2024-03-01 00:00:00. The time…
SQL Date Functions: DATE_ADD, DATEDIFF, EXTRACT
Date manipulation sits at the core of most business applications. Whether you’re calculating when a subscription expires, determining how long customers stay active, or grouping sales by quarter, you…
Read more →SQL - Convert Date to String
Converting dates to strings is one of those tasks that seems trivial until you’re debugging a report that shows ‘2024-01-15’ in production but ‘01/15/2024’ in development. Date formatting affects…
Read more →SQL - Convert String to Date
Every database developer eventually faces the same problem: dates stored as strings. Whether it’s data imported from CSV files, user input from web forms, legacy systems that predate proper date…
Read more →SQL - Calculate Age from Date of Birth
Calculating a person’s age from their date of birth seems straightforward until you actually try to implement it correctly. This requirement appears everywhere: user registration systems, insurance…
Read more →Spark SQL - Date and Timestamp Functions
Spark SQL handles three temporal data types: date (calendar date without time), timestamp (instant in time with timezone), and timestamp_ntz (timestamp without timezone, Spark 3.4+).
Scala - Date and Time Operations
The java.time package provides separate classes for dates, times, and combined date-times. Use LocalDate for calendar dates without time information and LocalTime for time without date context.
R lubridate - Date Arithmetic
Date arithmetic sounds simple until you actually try to implement it. Adding 30 days to January 15th is straightforward. Adding ‘one month’ is not—does that mean 28, 29, 30, or 31 days? What happens…
Read more →R - Date and Time Operations (as.Date, Sys.time)
Date and time operations sit at the core of most data analysis work. Whether you’re calculating customer tenure, analyzing time series trends, or simply filtering records by date range, you need…
Read more →PySpark - SQL Date Functions
Date manipulation is the backbone of data engineering. Whether you’re building ETL pipelines, analyzing time-series data, or creating reporting dashboards, you’ll spend significant time working with…
Read more →Pandas - Select Rows by Date Range
Before filtering by date ranges, ensure your date column is in datetime format. Pandas won’t recognize string dates for time-based operations.
Read more →Pandas - Filter DataFrame by Date Range
• Pandas offers multiple methods to filter DataFrames by date ranges, including boolean indexing, loc[], between(), and query(), each suited for different scenarios and performance requirements.
Pandas - Date Range Generation (date_range)
• pd.date_range() generates sequences of datetime objects with flexible frequency options, essential for time series analysis and data resampling operations
Pandas - Convert Timestamp to Date
• Pandas provides multiple methods to convert timestamps to dates: dt.date, dt.normalize(), and dt.floor(), each serving different use cases from extracting date objects to maintaining…
Pandas - Add/Subtract Days from Date
The most straightforward approach to adding or subtracting days uses pd.Timedelta. This method works with both individual datetime objects and entire Series.
How to Use Date Functions in MySQL
• MySQL stores dates and times in five distinct data types (DATE, DATETIME, TIMESTAMP, TIME, YEAR), each optimized for different use cases and storage requirements—choose DATETIME for most…
Read more →How to Use Date Functions in PostgreSQL
PostgreSQL provides four fundamental date and time types that serve distinct purposes. DATE stores calendar dates without time information, occupying 4 bytes. TIME stores time of day without date or…
Read more →How to Use Date Functions in SQLite
• SQLite doesn’t have a dedicated date type—dates are stored as TEXT (ISO 8601), REAL (Julian day), or INTEGER (Unix timestamp), making proper function usage critical for accurate queries
Read more →How to Filter by Date in Pandas
Date filtering is one of the most common operations in data analysis. Whether you’re analyzing sales trends, processing server logs, or building financial reports, you’ll inevitably need to slice…
Read more →Date and Time: Time Zones, UTC, and Libraries
Time handling has a well-earned reputation as one of programming’s most treacherous domains. The complexity stems from a collision between human political systems and the need for precise…
Read more →Date Functions in PySpark vs Pandas vs SQL
Every data engineer knows this pain: you write a date transformation in Pandas during exploration, then need to port it to PySpark for production, and finally someone asks for the equivalent SQL for…
Read more →