Update Metadata DB Derived.md

Author: pchemguy

Metadata DB Derived.md

@@ -8,7 +8,7 @@ permalink: /meta/db-derived-cte
 
 Extended parsed and structured metadata is available for table columns ([table_xinfo][]), foreign keys ([foreign_key_list][]), and indices ([index_list][] and [index_xinfo][]) via respective pragma functions. However, none of these PRAGMAs provide database-wide information. *index_xinfo* returns index-specific metadata. The three other PRAGMAs return a list of columns (all columns or columns participating in foreign keys or indices, respectively) for a particular table. Retrieval of database-wide metadata tables requires a combination of base queries.
 
-### Table Columns
+### Table columns
 
 Consider the *pragma_table_xinfo* table-valued function, which takes either the target table name as a string (not an identifier!) or a column identifier. In the latter case, each column value should contain a table name, and this option permits the construction of a query collecting database-wide column information. The first query retrieves the list of database tables (*tables*), and the second query (*columns*) uses *pragma_table_xinfo* with the retrieved table list in its JOIN clause to produce a database-wide column set. A combination of the two via either the subquery construct or common table expressions (CTEs) results in a relatively simple query, but it is instructive to follow the CTEs route. [Fig. 1](#TableColumnsCTE) shows a schematic structure of the CTEs query (left panel), which includes two subqueries discussed above. The right panel shows the corresponding CTEs code blocks.
 
@@ -35,7 +35,7 @@ The combined query below consists of the two CTEs blocks and the following main
 | classes_groups | 2   | super_group | TEXT    | 1       |            | 0  |
 
 
-### Debugging CTE queries
+### Debugging CTEs queries
 
 Well-structured CTEs queries provide several advantages for designing complex queries, particularly in SQLite. On the one hand, individual WITH members are convenient building blocks, as illustrated later. On the other hand, CTEs enable several debugging options, such as the ability of the main query after the WITH clause to interrogate any WITH clause member. For instance, in the example above, the last line `SELECT * FROM tables` verifies the output of the *tables* query.
 
@@ -50,7 +50,7 @@ The names of the WITH clause member query and its returned columns form the sign
 
 Additionally, given the output signature of the *tables* query and its semantics, it can now be reused as a code snippet.
 
-### Foreign Keys
+### Foreign keys
 
 Both *pragma_foreign_key_list* and *pragma_index_list* return tables containing a row for each unique (column, index/FK) combination. The Foreign Keys query starts with a copy of the *table* block. The *columns* block, however, needs adjustments to take into account the signature and semantics of the returned table (*fkey_columns*). Furthermore, for composite indices/FKs, one row is returned for each participating column. Often, it is more convenient to have one row per index/FK, meaning that an additional WITH block is necessary to collapse rows corresponding to the same composite index/FK, as shown in [Fig. 2](#ForeignKeys).