1. Introduction

+ +

Every SQLite database contains a single "schema table" that stores the +schema for that database. The schema for a database is a description of +all of the other tables, indexes, triggers, and views that are +contained within the database. The schema table looks like this: + +

+CREATE TABLE sqlite_schema(
+  type text,
+  name text,
+  tbl_name text,
+  rootpage integer,
+  sql text
+);
+

+ +

The sqlite_schema table contains one row for each table, index, view, +and trigger (collectively "objects") in the schema, except there +is no entry for the sqlite_schema table itself. See the +schema storage subsection of the file format documentation for +additional information on how SQLite uses the sqlite_schema table +internally. + +

2. Alternative Names

+ +

The schema table can always be referenced using the name "sqlite_schema", +especially if qualifed by the schema name like +"main.sqlite_schema" or "temp.sqlite_schema". But for historical +compatibility, some alternative names are also recognized, including: + +

sqlite_master +
sqlite_temp_schema +
sqlite_temp_master +

+ +

+Alternatives (2) and (3) only work for the TEMP database associated +with each database connection, but alternative (1) works anywhere. +For historical reasons, callbacks from the sqlite3_set_authorizer() +interface always refer to the schema table using names (1) or (3). + +

3. Interpretation Of The Schema Table

+ +

The meanings of the fields of the schema table are as follows: + +

type

The sqlite_schema.type column will be one +of the following text strings: 'table', 'index', 'view', or 'trigger' +according to the type of object defined. The 'table' string is used +for both ordinary and virtual tables.

name

+

The sqlite_schema.name column will hold the name of the object. +UNIQUE and PRIMARY KEY constraints on tables cause SQLite to create +internal indexes with names of the form "sqlite_autoindex_TABLE_N" +where TABLE is replaced by the name of the table that contains the +constraint and N is an integer beginning with 1 and increasing by one +with each constraint seen in the table definition. +In a WITHOUT ROWID table, there is no sqlite_schema entry for the +PRIMARY KEY, but the "sqlite_autoindex_TABLE_N" name is set aside +for the PRIMARY KEY as if the sqlite_schema entry did exist. This +will affect the numbering of subsequent UNIQUE constraints. +The "sqlite_autoindex_TABLE_N" name is never allocated for an +INTEGER PRIMARY KEY, either in rowid tables or WITHOUT ROWID tables. +

tbl_name

The sqlite_schema.tbl_name column holds the name of a table or view +that the object is associated with. For a table or view, the +tbl_name column is a copy of the name column. For an index, the tbl_name +is the name of the table that is indexed. For a trigger, the tbl_name +column stores the name of the table or view that causes the trigger +to fire.

rootpage

The sqlite_schema.rootpage column stores the page number of the root +b-tree page for tables and indexes. For rows that define views, triggers, +and virtual tables, the rootpage column is 0 or NULL.

sql

The sqlite_schema.sql column stores SQL text that describes the +object. This SQL text is a CREATE TABLE, CREATE VIRTUAL TABLE, +CREATE INDEX, +CREATE VIEW, or CREATE TRIGGER statement that if evaluated against +the database file when it is the main database of a database connection +would recreate the object. The text is usually a copy of the original +statement used to create the object but with normalizations applied so +that the text conforms to the following rules: + +

The CREATE, TABLE, VIEW, TRIGGER, and INDEX keywords at the beginning +of the statement are converted to all upper case letters. +
The TEMP or TEMPORARY keyword is removed if it occurs after the +initial CREATE keyword. +
Any database name qualifier that occurs prior to the name of the +object being created is removed. +
Leading spaces are removed. +
All spaces following the first two keywords are converted into a single +space. +

+ +

The text in the sqlite_schema.sql column is a copy of the original +CREATE statement text that created the object, except normalized as +described above and as modified by subsequent ALTER TABLE statements. +The sqlite_schema.sql is NULL for the internal indexes that are +automatically created by UNIQUE or PRIMARY KEY constraints.

+ +

4. Creation and Modification Of The Schema Table

+ +

SQLite creates the schema table upon database creation and modifies +its content as SQLite users submit DDL statements for execution. There +is no need for users to modify it under normal circumstances, and they +bear the risk of database corruption if they do modify it. +

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