SQL curriculum

Start here — the syntax and mental models everything else builds on.

1. 1

   Query basics

   ~5 min · 1 lesson

   Pull exactly the columns you need out of any table.

   SELECTFROMASDISTINCT

   • SELECT queriesup next5m
2. 2

   Filtering & sorting

   ~14 min · 2 lessons

   Find the rows that matter — e.g. UK customers who signed up this year, newest first.

   WHEREORDER BYLIMITIS NULL

   • Filtering and sorting7m
   • NULLs and COALESCE7m
3. 3

   Aggregation

   ~8 min · 1 lesson

   Answer business questions like total sales per country or average order value.

   COUNTSUMAVGGROUP BYHAVING

   • Aggregation and GROUP BY8m

Combine data from several places and reshape it into answers.

1. 1

   Joins

   ~15 min · 2 lessons

   Combine customers, orders and products into one answer.

   JOINLEFT JOINUNIONself join

   • Joins9m
   • UNION, INTERSECT and EXCEPT6m
2. 2

   Subqueries & CTEs

   ~18 min · 2 lessons

   Break a hard question into small named steps.

   IN (…)EXISTSWITHRECURSIVE

   • Subqueries and CTEs9m
   • Recursive CTEs9m
3. 3

   Dates & text

   ~25 min · 3 lessons

   Group sales by month, clean up names and label rows with rules.

   strftimeSUBSTRLOWERCASE WHEN

   • Working with dates9m
   • String functions8m
   • CASE and conditional aggregation8m

The techniques that show up in real interviews and real pipelines.

1. 1

   Window functions

   ~22 min · 2 lessons

   Rank products, compute running totals and compare to the previous row.

   OVERPARTITION BYRANKLAG

   • Window functions11m
   • Frames, LAG and LEAD11m
2. 2

   Analytics patterns

   ~31 min · 3 lessons

   Build the retention, growth and top-N reports analysts ship weekly.

   cohortsMoM growthtop-N

   • Cohorts and retention12m
   • Growth and funnels10m
   • Top N per group9m
3. 3

   Query performance

   ~17 min · 2 lessons

   Explain why a query is slow and make it fast.

   INDEXEXPLAINrewrites

   • How indexes work8m
   • Reading a query plan9m