Create SM ASCII IDs.md

Author: pchemguy

SM ASCII IDs.md

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+---
+layout: default
+title: ASCII IDs
+nav_order: 4
+parent: String Manipulation
+permalink: /strings/ascii-id
+---
+
+The following query generates random eight-character-long ASCII IDs (*id_counts*.*id_counter* pieces) using the specified alphabet (*char_templates*). The dash and underscore characters extend the alphanumeric alphabet to 64 characters allowing the selection of the six least significant bits from a random 64-bit number via bitwise AND (instead of *mod*). The *ids* block generates a 64-bit integer representation of the same ID. Saving character code before grouping in *ascii_ids* would not work because the query optimizer tends to rerun the query, executing the *random* function and generating the character and character code independently. The intermediate table aggregation operation prevents this optimization.
+
+~~~sql
+WITH
+    id_counts(id_counter) AS (VALUES (3)),
+    json_templates AS (SELECT '[' || replace(hex(zeroblob(id_counter*8-1)), '00', '0,') || '0]' AS json_template FROM id_counts),
+    char_templates(char_template) AS (VALUES ('-0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz_')),
+    ascii_ids AS (
+        SELECT group_concat(substr(char_template, (random() & 63) + 1, 1), '') AS ascii_id, "key"/8 AS counter
+        FROM char_templates, json_templates, json_each(json_templates.json_template) AS terms
+		GROUP BY counter
+	),
+	ids AS (
+		SELECT counter, ascii_id,
+			   (unicode(substr(ascii_id, 1, 1)) << 8*7) +
+			   (unicode(substr(ascii_id, 2, 1)) << 8*6) +
+			   (unicode(substr(ascii_id, 3, 1)) << 8*5) +
+			   (unicode(substr(ascii_id, 4, 1)) << 8*4) +
+			   (unicode(substr(ascii_id, 5, 1)) << 8*3) +
+			   (unicode(substr(ascii_id, 6, 1)) << 8*2) +
+			   (unicode(substr(ascii_id, 7, 1)) << 8*1) +
+			   (unicode(substr(ascii_id, 8, 1)) << 8*0) AS bin_id
+		FROM ascii_ids
+	)
+SELECT * FROM ids;
+~~~
+
+**Sample output**
+
+| counter | ascii_id | bin_id              |
+|---------|----------|---------------------|
+| 0       | qszS_Wed | 8175012247544227167 |
+| 1       | HwrjLnvG | 5221768093833786951 |
+| 2       | bXHJexP0 | 7086493498034638896 |