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03 · Building Your First Visualization

With Orders connected (Module 2), it's time to build an actual worksheet. This module walks through the drag-and-drop mechanics — Columns/Rows shelves, the Marks card, and the Show Me panel — by building a bar chart of total Sales by Region, then verifying the numbers against the hand calculation from Module 1's exercise.

1. From Data Source to Worksheet

  1. Click the Sheet 1 tab at the bottom of the screen (or Worksheet > New Worksheet) to leave the Data Source page and reach a blank canvas.
  2. The Data pane on the left lists every field from Orders, split into Dimensions (Region, Category, Product, Order Date — blue) and Measures (Sales, Quantity, Profit — green), matching the roles from Module 1.
  3. The main canvas is empty except for the Columns and Rows shelves along the top, and the Marks card on the left showing the current mark type (defaults to Automatic).

2. Building total Sales by Region (bar chart)

  1. Drag Region from the Data pane onto the Columns shelf. Tableau adds a header for each distinct region (Central, East, West) along the top of the canvas — nothing is plotted yet since there's no measure.
  2. Drag Sales from the Data pane onto the Rows shelf. Tableau automatically aggregates it as SUM(Sales) (the default aggregation for a measure) and draws one bar per region, since the Marks card mark type auto-switched to Bar.
  3. Read the bar heights against your Module 1 hand calculation: East should total 2210 (1200 + 60 + 950), West should total 3750 (450 + 2200 + 1100), Central should total 920 (800 + 120). Hover over any bar to see the exact value in the tooltip Tableau generates automatically.
  4. If the bars aren't sorted by height, click the sort descending icon that appears in the toolbar above the canvas (or on the Region axis header on hover) to rank regions by total Sales at a glance.

3. The Show Me panel

  1. Click Show Me (top-right of the window, a small grid icon) to open a panel of chart-type thumbnails. Tableau greys out any chart type that doesn't fit the fields currently on your shelves and highlights ones that do — with Region (dimension) and SUM(Sales) (measure) already placed, the bar chart thumbnail is highlighted as the best match.
  2. Show Me is a shortcut, not a requirement — everything it produces you could also build manually via Columns/Rows/Marks, which is why this module built the bar chart by hand first. Use Show Me once you already know roughly what chart you want and want Tableau to place the fields for you.
  3. Try clicking a different highlighted thumbnail (e.g. horizontal bars) to see Tableau instantly rebuild the same view in a new orientation — confirming that the underlying data reference doesn't change, only the shelf placement.

4. The Marks card in more depth

  1. The Marks card has a dropdown at the top (mark type: Automatic, Bar, Line, Circle, Shape, and more) and rows below it: Color, Size, Label, Detail, Tooltip.
  2. Drag Category onto Color on the Marks card. Each region's single bar splits into a stacked bar of segments, one color per category (Furniture, Electronics, Office Supplies) — a fast way to add a second dimension without changing shelves.
  3. Drag SUM(Profit) onto Label. Each stacked segment now shows its profit value directly on the mark — useful for a quick presentation view, though it can get visually noisy with more categories or regions than this example.
  4. Remove a field from any shelf or the Marks card at any time by dragging it off the shelf (or right-click → Remove) — nothing here is destructive to the underlying data, only to this worksheet's view.

5. Aggregation matters

  1. Right-click SUM(Sales) on the Rows shelf → note the Measure submenu lists other aggregations: Average, Median, Count, Minimum, Maximum, and more.
  2. Switch it to Average. The East bar now shows 736.67 (2210 / 3 orders) instead of 2210 — the same field, a completely different story, which is why confirming the aggregation shown (SUM vs AVG) is the first thing to check when a number on a real dashboard looks surprising.
  3. Switch back to Sum before moving on, since Module 4 assumes SUM(Sales) as the baseline.

How It Actually Works

Right-clicking SUM(Sales) → Measure → Average doesn't relabel the existing bar — it rewrites the aggregate function inside VizQL's generated query from SUM(Sales) to AVG(Sales) and re-runs it, which is why the whole chart, including its axis scale, redraws rather than just its label:

  1. For the East bar: SUM(Sales) over the three East rows (1200, 60, 950) is 2210 — the query pattern is SELECT Region, SUM(Sales) FROM Orders WHERE Region='East' GROUP BY Region. Switching to AVG(Sales) changes the generated aggregate to SELECT Region, AVG(Sales) FROM Orders WHERE Region='East' GROUP BY Region, which evaluates to 2210 / 3 = 736.67 — a different SQL function over the same underlying rows, not a post-processing division applied to the displayed bar.
  2. This distinguishes a regular aggregation switch (this module) from a table calculation (Module 8): AVG here is computed by the query engine itself, from the raw rows, in one pass — it isn't dependent on what else is in the view. A table calc, by contrast, runs after the aggregate query returns, operating only on the numbers already visible — which is why Module 8 needs "Compute Using" and this module doesn't.
  3. Dragging Category onto Color (Exercise) adds Category to the GROUP BY clause without moving it to a shelf that produces new header rows — Color is VizQL's way of saying "subdivide each existing mark by this dimension, encoded visually, not as a new axis position." The underlying query becomes GROUP BY Region, Category, producing one mark per (Region, Category) pair, each colored distinctly, stacked or placed within its Region's bar depending on the mark type.

Cheat sheet

Action How
Add a dimension to slice the view Drag to Columns or Rows
Add/aggregate a measure Drag to Columns or Rows (defaults to SUM)
Change chart type quickly Show Me panel (top right)
Change chart type manually Marks card dropdown (Automatic/Bar/Line/…)
Split bars by a second dimension Drag dimension onto Color
Show values on marks Drag measure onto Label
Change a measure's aggregation Right-click field on shelf → Measure
See exact value Hover for tooltip

Exercise

Build the Region × Sales bar chart as described, then add Category to Color and SUM(Quantity) to Label instead of Profit. Identify, from the resulting labels, which single (region, category) combination sold the highest quantity of items — then verify it against the raw Orders table from Module 1 by hand.