SQL Lesson 7: Subqueries
Use a query inside a query: compare with an average, filter with IN and NOT IN, find the row with the maximum, query a…
Read article →Atul Vij
SQL Lesson 6: JOINs — Combining Tables
SQL Lesson 6: JOINs — Combining Tables
Combine tables with JOIN: primary and foreign keys, INNER JOIN, table aliases, joining three tables, LEFT JOIN to find missing matches, and the duplicate-row…
Read article →SQL Lesson 5: GROUP BY and HAVING
SQL Lesson 5: GROUP BY and HAVING
Get totals per group with GROUP BY — customers per region, orders per status, sales per month — filter groups with HAVING, and know…
Read article →SQL Lesson 4: COUNT, SUM, AVG, MIN and MAX
SQL Lesson 4: COUNT, SUM, AVG, MIN and MAX
Summarise data with aggregate functions: COUNT(*) vs COUNT(column), SUM, AVG with ROUND, MIN and MAX on numbers and dates, filtering before aggregating, and how…
Read article →SECOND Function in Excel: Second From a Time
SECOND Function in Excel: Second From a Time
DateLevel: BeginnerAvailable in: Excel 2007+SECOND returns 0–59. Mostly used to strip seconds from machine.
Read article →SQL Lesson 3: ORDER BY and LIMIT
SQL Lesson 3: ORDER BY and LIMIT
Sort SQL results with ORDER BY, ascending and descending, by several columns and by calculated values; get top-N lists with LIMIT, and understand why…
Read article →SQL Lesson 2: WHERE — Filtering Rows
SQL Lesson 2: WHERE — Filtering Rows
Filter rows in SQL with WHERE: comparison operators, AND/OR with brackets, IN, BETWEEN, LIKE with % and _, and IS NULL — the SQL…
Read article →SQL Lesson 1: SELECT — Reading Data
SQL Lesson 1: SELECT — Reading Data
Your first SQL queries: what tables, rows and columns are, install DB Browser for SQLite, SELECT columns, SELECT *, calculated columns with AS, DISTINCT…
Read article →HOUR Function in Excel: Hour From a Time
HOUR Function in Excel: Hour From a Time
HOUR returns 0–23 from a time or date-time. The quickest way to group call-centre or sales data by hour of day.
Read article →TIME Function in Excel: Build a Time From Hours, Minutes, Seconds
TIME Function in Excel: Build a Time From Hours, Minutes, Seconds
TIME creates a time value. Excel stores time as a fraction of a day: 12:00 is 0.5, 6:00 is 0.25.
Read article →NOW Function in Excel: Current Date and Time
NOW Function in Excel: Current Date and Time
NOW returns the current date and time and updates every time the sheet recalculates. For a timestamp that stays fixed, press Ctrl+; then Space…
Read article →VARP Function in Excel: Population Variance (Older Name)
VARP Function in Excel: Population Variance (Older Name)
VARP gives the variance of a whole population. It is a compatibility function: Excel keeps it so workbooks from Excel 2007 and earlier still…
Read article →