Finish query package for now

database/query/README.md

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+# Query
+
+## Control Flow
+
+- Grouping with `(` and `)`
+- Chaining with `and` and `or`
+  - _NO_ mixing! Be explicit and use grouping.
+- Negation with `not`
+  - in front of expression for group: `not (...)`
+  - inside expression for clause: `name not matches "^King "`
+
+## Selectors
+
+Supported by all feeders:
+- root level field: `field`
+- sub level field: `field.sub`
+- array/slice/map access: `map.0`
+- array/slice/map length: `map.#`
+
+Please note that some feeders may have other special characters. It is advised to only use alphanumeric characters for keys.
+
+## Operators
+
+| Name | Textual | Req. Type | Internal Type | Compared with |
+|---|---|---|---|
+| Equals | `==` | int | int64 | `==` |
+| GreaterThan | `>` | int | int64 | `>` |
+| GreaterThanOrEqual | `>=` | int | int64 | `>=` |
+| LessThan | `<`  | int | int64 | `<` |
+| LessThanOrEqual | `<=` | int | int64 | `<=` |
+| FloatEquals | `f==` | float | float64 | `==` |
+| FloatGreaterThan | `f>` | float | float64 | `>` |
+| FloatGreaterThanOrEqual | `f>=` | float | float64 | `>=` |
+| FloatLessThan | `f<` | float | float64 | `<` |
+| FloatLessThanOrEqual | `f<=` | float | float64 | `<=` |
+| SameAs | `sameas`, `s==` | string | string | `==` |
+| Contains | `contains`, `co` | string | string | `strings.Contains()` |
+| StartsWith | `startswith`, `sw` | string | string | `strings.HasPrefix()` |
+| EndsWith | `endswith`, `ew` | string | string | `strings.HasSuffix()` |
+| In | `in` | string | string | for loop with `==` |
+| Matches | `matches`, `re` | string | int64 | `regexp.Regexp.Matches()` |
+| Is | `is` | bool* | bool | `==` |
+| Exists | `exists`, `ex` | any | n/a | n/a |
+
+\*accepts strings: 1, t, T, TRUE, true, True, 0, f, F, FALSE
+
+## Escaping
+
+If you need to use a control character within a value (ie. not for controlling), escape it with `\`.
+It is recommended to wrap a word into parenthesis instead of escaping control characters, when possible.
+
+| Location | Characters to be escaped |
+|---|---|
+| Within parenthesis (`"`) | `"`, `\` |
+| Everywhere else | `(`, `)`, `"`, `\`, `\t`, `\r`, `\n`, ` ` (space) |