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(This page was last modified on [lrange $rcsid 3 4] GMT)
" puts {The SQLite library understands most of the standard SQL language. But it does omit some features while at the same time adding a few features of its own. This document attempts to describe percisely what parts of the SQL language SQLite does and does not support.
In all of the syntax diagrams that follow, literal text is shown in bold blue. Non-terminal symbols are shown in italic red. Operators that are part of the syntactic markup itself are shown in black roman.
This document is just an overview of the SQL syntax implemented by SQLite. Many low-level productions are omitted. For detailed information on the language that SQLite understands, refer to the source code.
SQLite implements the follow SQL commands:
Details on the implementation of each command are provided in the sequel.
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" } Section COPY copy Syntax {sql-statement} { COPY$text
The COPY command is an extension used to load large amounts of data into a table. It is modeled after a similar command found in PostgreSQL. In fact, the SQLite COPY command is specifically designed to be able to read the output of the PostgreSQL dump utility pg_dump so that data can be easily transferred from PostgreSQL into SQLite.
The table-name is the name of an existing table which is to be filled with data. The filename is a string or identifier that names a file from which data will be read. The filename can be the STDIN to read data from standard input.
Each line of the input file is converted into a single record in the table. Columns are separated by tabs. If a tab occurs as data within a column, then that tab is preceded by a baskslash "\" character. A baskslash in the data appears as two backslashes in a row.
When the input data source is STDIN, the input can be terminated by a line that contains only a baskslash and a dot:} puts "\"[Operator \\.]\".
" Section {CREATE INDEX} createindex Syntax {sql-statement} { CREATE INDEXThe CREATE INDEX command consists of the keywords "CREATE INDEX" followed by the name of the new index, the keyword "ON" the name of a previously created table that is to be indexed, and a parenthesized list of names of columns in the table that are used for the index key. Each column name can be followed by one of the "ASC" or "DESC" keywords to indicate sort order, but since GDBM does not implement ordered keys, these keywords are ignored.
There are no arbitrary limits on the number of indices that can be attached to a single table, nor on the number of columns in an index.
The exact text of each CREATE INDEX statement is stored in the sqlite_master table. Everytime the database is opened, all CREATE INDEX statements are read from the sqlite_master table and used to regenerate SQLite's internal representation of the index layout.
} Section {CREATE TABLE} {createtable} Syntax {sql-command} { CREATE TABLEA CREATE TABLE statement is basically the keywords "CREATE TABLE" followed by the name of a new table and a parenthesized list of column definitions and constraints. The table name can be either an identifier or a string. The only reserved table name is "sqlite_master" which is the name of the table that records the database schema.
Each column definition is the name of the column followed by the datatype for that column, then one or more optional column constraints. The datatype for the column is ignored. All information is stored as null-terminated strings. The constraints are also ignored, except that the PRIMARY KEY constraint will cause an index to be automatically created that implements the primary key and the DEFAULT constraint which specifies a default value to use when doing an INSERT. The name of the primary key index will be the table name with "__primary_key" appended. The index used for a primary key does not show up in the sqlite_master table, but a GDBM file is created for that index.
There are no arbitrary limits on the size of columns, on the number of columns, or on the number of constraints in a table.
The exact text of each CREATE TABLE statement is stored in the sqlite_master table. Everytime the database is opened, all CREATE TABLE statements are read from the sqlite_master table and used to regenerate SQLite's internal representation of the table layout.
} Section DELETE delete Syntax {sql-statement} { DELETE FROMThe DELETE command is used to remove records from a table. The command consists of the "DELETE FROM" keywords followed by the name of the table from which records are to be removed.
Without a WHERE clause, all rows of the table are removed. If a WHERE clause is supplied, then only those rows that match the expression are removed.
} Section {DROP INDEX} dropindex Syntax {sql-command} { DROP INDEXThe DROP INDEX statement consists of the keywords "DROP INDEX" followed by the name of the index. The index named is completely removed from the disk. The only way to recover the index is to reenter the appropriate CREATE INDEX command.
} Section {DROP TABLE} droptable Syntax {sql-command} { DROP TABLEThe DROP TABLE statement consists of the keywords "DROP TABLE" followed by the name of the table. The table named is completely removed from the disk. The table can not be recovered. All indices associated with the table are also deleted.
} Section EXPLAIN explain Syntax {sql-statement} { EXPLAINThe EXPLAIN command modifier is a non-standard extension. The idea comes from a similar command found in PostgreSQL, but the operation is completely different.
If the EXPLAIN keyword appears before any other SQLite SQL command then instead of actually executing the command, the SQLite library will report back the sequence of virtual machine instructions it would have used to execute the command had the EXPLAIN keyword not been present. For additional information about virtual machine instructions see the architecture description or the documentation on available opcodes for the virtual machine.
} Section expression expr Syntax {expression} {