chore: useful-sql.md to /docs (#610)

1 files changed, 132 insertions, 0 deletions

diff --git a/docs/useful-sql.md b/docs/useful-sql.md
new file mode 100644
index 0000000..13eca54
--- /dev/null
+++ b/docs/useful-sql.md
@@ -0,0 +1,132 @@
+# useful-sql.md
+
+## Useful SQL snippets:
+
+### Table of Contents
+  * [Introduction](#introduction)
+  * [Loot and Reference Loot Issues](#loot-and-reference-loot-issues)
+    + [Find what creatures drop an item directly](#find-what-creatures-drop-an-item-directly)
+    + [Find which RLTs an item is in](#find-which-rlts-an-item-is-in)
+    + [Find which creatures share a RLT](#find-which-creatures-share-a-rlt)
+    + [Find number of items and level statistics for items in a given RLT](#find-number-of-items-and-level-statistics-for-items-in-a-given-rlt)
+    + [Recursively find an item by name](#recursively-find-an-item-by-name)
+  * [Miscellaneous Issues](#miscellaneous-issues)
+    + [Find creature information from a spawn GUID](#find-creature-information-from-a-spawn-guid)
+    + [Find all static creatures given a name](#find-all-static-creatures-given-a-name)
+    + [Find creatures that use a certain spell](#find-creatures-that-use-a-certain-spell)
+    + [Find average wander distance for a creature](#find-average-wander-distance-for-a-creature)
+    + [Find other members of a node pool](#find-other-members-of-a node-pool)
+
+### Introduction
+These SQL queries are intended to be fast and easy-to-use tools that can help identify and troubleshoot problems in the AzerothCore database. They're here to be a quick reference to help when looking at DB-related problems. If anyone else has any similar useful queries, let me know and I'll add them. Similarly, if you have a common problem for which you'd like a query written, feel free to get in touch.
+
+### Loot and Reference Loot Issues
+
+#### Find what creatures drop an item directly
+Note that this doesn't count items dropped from RLTs.
+```SQL
+SELECT ct.name, clt.chance, ct.maxlevel, it.ItemLevel
+FROM `creature_template` ct
+JOIN `creature_loot_template` clt ON ct.lootid = clt.entry
+JOIN `item_template` it ON clt.item = it.entry
+WHERE it.entry = XXXXX;
+```
+
+#### Find which RLTs an item is in
+```SQL
+SELECT rlt.entry, it.entry, it.name
+FROM `reference_loot_template` rlt
+JOIN `item_template` it ON rlt.Item = it.entry
+WHERE it.entry = XXXXX;
+```
+
+#### Find which creatures share a RLT
+Non-recursive.
+```SQL
+SELECT distinct ct.entry, ct.name
+FROM `creature_template` ct
+JOIN `creature_loot_template` clt ON ct.lootid = clt.entry
+WHERE clt.Reference = XXXXX;
+```
+
+#### Find number of items and level statistics for items in a given RLT
+This is useful when determining which creatures should have a particular RLT in their drop tables.
+```SQL
+SELECT COUNT(rlt.Item), MIN(it.ItemLevel), MAX(it.ItemLevel), AVG(it.ItemLevel)
+FROM `item_template` it 
+JOIN `reference_loot_template` rlt ON it.entry = rlt.item 
+WHERE rlt.entry = XXXXX;
+```
+
+#### Recursively find an item by name
+Note this is complex enough that Keira won't run it properly - you will need to run it from a MySQL command prompt. Thanks to @anguaive for this one.
+```SQL
+SET @ITEM_NAME := 'insert name of item here';
+SET @ITEM_ID := (SELECT `entry` FROM `item_template` WHERE `name` = @ITEM_NAME);
+
+SELECT DISTINCT ct.name AS `creature`, @ITEM_NAME as `item` FROM (
+    WITH RECURSIVE cte (`entry`, `item`, `reference`) AS (
+    SELECT `entry`, `item`, `reference`
+    FROM `reference_loot_template`
+    WHERE `item` = @ITEM_ID
+    UNION ALL
+    SELECT r.entry, r.item, r.reference
+    FROM `reference_loot_template` r
+    INNER JOIN cte
+    ON r.reference = cte.entry
+    )
+    SELECT clt.entry
+    FROM cte
+    JOIN `creature_loot_template` clt ON clt.reference = cte.entry
+    UNION ALL
+    SELECT entry
+    FROM
+    `creature_loot_template` 
+    WHERE item = @ITEM_ID
+) AS q
+JOIN `creature_template` ct ON ct.lootid = q.entry
+ORDER BY ct.name;
+```
+
+### Miscellaneous Issues
+#### Find creature information from a spawn GUID
+Bug reports sometimes just reference a GUID with no other information about an NPC. This will find the creature a GUID belongs to.
+```SQL
+SELECT ct.entry, ct.name, ct.minlevel, ct.maxlevel
+FROM `creature_template` ct 
+JOIN `creature` c ON ct.entry = c.id
+WHERE c.guid = XXXXX;
+```
+
+#### Find all static creatures given a name
+You can just use part of the NPC's name (as here, 'Gordunni') and it will find all NPCs with that string in their name.
+```SQL
+SELECT c.guid, ct.name
+FROM `creature` c
+JOIN `creature_template` ct ON ct.entry = c.id
+WHERE c.movementtype = 0 AND ct.name LIKE '%gordunni%';
+```
+
+#### Find creatures that use a certain spell
+Note this is a bit rough and ready, and only works if the spell is in their first action slot. In this case, XXXX is the spell ID.
+```SQL
+SELECT ct.entry, ct.name, ct.maxlevel, ss.action_param1
+FROM `creature_template` ct
+JOIN `smart_scripts` ss ON ct.entry = ss.entryorguid
+WHERE ss.action_param1 = XXXXX;
+```
+
+#### Find average wander distance for a creature
+Handy for fixing static creatures.
+```SQL
+SELECT c.id, AVG(c.wander_distance)
+FROM `creature` c
+WHERE c.id = XXXX;
+```
+
+#### Find other members of a node pool
+Given a node GUID, find if it belongs to a node pool and list the other members.
+```SQL
+SELECT * FROM `pool_gameobject` WHERE `pool_entry` IN (
+SELECT `pool_entry` from `pool_gameobject` WHERE guid = XXXX);
+```