docs(book): add a section about division operators (#3603)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Maximilian Roos <[email protected]>

web/book/src/reference/syntax/operators.md

@@ -34,6 +34,25 @@ operations and for function calls (see the discussion below.)
 |             or | <code>\|\|</code>           |     9      | left-to-right |
 |  function call |                             |     10     |               |
 
+## Division and integer division
+
+The `/` operator performs division that always returns a float value, while the
+`//` operator does integer division (truncated division) that always returns an
+integer value.
+
+```prql
+prql target:sql.sqlite
+
+from [
+  {a = 5, b = 2},
+  {a = 5, b = -2},
+]
+select {
+  div_out = a / b,
+  int_div_out = a // b,
+}
+```
+
 ## Coalesce
 
 We can coalesce values with an `??` operator. Coalescing takes either the first

web/book/tests/documentation/snapshots/documentation__book__reference__syntax__operators__division-and-integer-division__0.snap

@@ -0,0 +1,20 @@
+---
+source: web/book/tests/documentation/book.rs
+expression: "prql target:sql.sqlite\n\nfrom [\n  {a = 5, b = 2},\n  {a = 5, b = -2},\n]\nselect {\n  div_out = a / b,\n  int_div_out = a // b,\n}\n"
+---
+WITH table_0 AS (
+  SELECT
+    5 AS a,
+    2 AS b
+  UNION
+  ALL
+  SELECT
+    5 AS a,
+    -2 AS b
+)
+SELECT
+  (a * 1.0 / b) AS div_out,
+  ROUND(ABS(a / b) - 0.5) * SIGN(a) * SIGN(b) AS int_div_out
+FROM
+  table_0
+