Candidate keys: unique keys per table, with recommendations

views/i_s/_schema_unique_keys.sql

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+-- 
+-- Unique keys: listing of all unique keys aith aggregated column names and additional data
+-- 
+CREATE OR REPLACE
+  ALGORITHM = TEMPTABLE
+  DEFINER = 'root'@'localhost'
+  SQL SECURITY INVOKER
+VIEW _schema_unique_keys AS
+  SELECT
+    TABLE_SCHEMA,
+    TABLE_NAME,
+    INDEX_NAME,
+    COUNT(*) AS COUNT_COLUMN_IN_INDEX,
+    IF(SUM(NULLABLE = 'YES') > 0, 1, 0) AS has_nullable,
+    IF(INDEX_NAME = 'PRIMARY', 1, 0) AS is_primary,
+    GROUP_CONCAT(COLUMN_NAME ORDER BY SEQ_IN_INDEX ASC) AS COLUMN_NAMES,
+    SUBSTRING_INDEX(GROUP_CONCAT(COLUMN_NAME ORDER BY SEQ_IN_INDEX ASC), ',', 1) AS FIRST_COLUMN_NAME
+  FROM INFORMATION_SCHEMA.STATISTICS
+  WHERE NON_UNIQUE=0
+  GROUP BY TABLE_SCHEMA, TABLE_NAME, INDEX_NAME
+;
+

views/i_s/schema_candidate_keys.sql

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+-- 
+-- Candidate keys: listing of prioritized candidate keys: keys which are UNIQUE, by order of best-use. 
+-- 
+
+CREATE OR REPLACE
+  ALGORITHM = TEMPTABLE
+  DEFINER = 'root'@'localhost'
+  SQL SECURITY INVOKER
+VIEW schema_candidate_keys AS
+SELECT
+  COLUMNS.TABLE_SCHEMA AS table_schema,
+  COLUMNS.TABLE_NAME AS table_name,
+  _schema_unique_keys.INDEX_NAME AS index_name,
+  _schema_unique_keys.has_nullable AS has_nullable,
+  _schema_unique_keys.is_primary AS is_primary,
+  _schema_unique_keys.COLUMN_NAMES AS column_names,
+  _schema_unique_keys.COUNT_COLUMN_IN_INDEX AS count_column_in_index,
+  COLUMNS.DATA_TYPE AS data_type,
+  COLUMNS.CHARACTER_SET_NAME AS character_set_name,
+  (CASE IFNULL(CHARACTER_SET_NAME, '')
+      WHEN '' THEN 0
+      ELSE 1
+  END << 20
+  )
+  + (CASE LOWER(DATA_TYPE)
+    WHEN 'tinyint' THEN 0
+    WHEN 'smallint' THEN 1
+    WHEN 'int' THEN 2
+    WHEN 'timestamp' THEN 3
+    WHEN 'bigint' THEN 4
+    WHEN 'datetime' THEN 5
+    ELSE 9
+  END << 16
+  ) + (COUNT_COLUMN_IN_INDEX << 0
+  ) AS candidate_key_rank_in_table  
+FROM 
+  INFORMATION_SCHEMA.COLUMNS 
+  INNER JOIN _schema_unique_keys ON (
+    COLUMNS.TABLE_SCHEMA = _schema_unique_keys.TABLE_SCHEMA AND
+    COLUMNS.TABLE_NAME = _schema_unique_keys.TABLE_NAME AND
+    COLUMNS.COLUMN_NAME = _schema_unique_keys.FIRST_COLUMN_NAME
+  )
+ORDER BY   
+  COLUMNS.TABLE_SCHEMA, COLUMNS.TABLE_NAME, candidate_key_rank_in_table
+;
+

views/i_s/schema_candidate_keys_recommended.sql

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+-- 
+-- Candidate keys: listing of prioritized candidate keys: keys which are UNIQUE, by order of best-use. 
+-- 
+
+CREATE OR REPLACE
+  ALGORITHM = TEMPTABLE
+  DEFINER = 'root'@'localhost'
+  SQL SECURITY INVOKER
+VIEW schema_candidate_keys_recommended AS
+SELECT
+  table_schema,
+  table_name,
+  SUBSTRING_INDEX(GROUP_CONCAT(index_name ORDER BY candidate_key_rank_in_table ASC), ',', 1) AS recommended_index_name,
+  CAST(SUBSTRING_INDEX(GROUP_CONCAT(has_nullable ORDER BY candidate_key_rank_in_table ASC), ',', 1) AS UNSIGNED INTEGER) AS has_nullable,
+  CAST(SUBSTRING_INDEX(GROUP_CONCAT(is_primary ORDER BY candidate_key_rank_in_table ASC), ',', 1) AS UNSIGNED INTEGER) AS is_primary,
+  CAST(SUBSTRING_INDEX(GROUP_CONCAT(count_column_in_index ORDER BY candidate_key_rank_in_table ASC), ',', 1) AS UNSIGNED INTEGER) AS count_column_in_index,
+  SUBSTRING_INDEX(GROUP_CONCAT(column_names ORDER BY candidate_key_rank_in_table ASC SEPARATOR '\n'), '\n', 1) AS column_names
+FROM 
+  schema_candidate_keys
+GROUP BY
+  table_schema, table_name
+ORDER BY   
+  table_schema, table_name
+;