SQLite3 Backend Reference

SOCI backend for accessing SQLite 3 database.

Prerequisites

Supported Versions

The oldest tested SQLite3 version that SOCI was tested with was 3.1.3 and the latest tested version is 3.49.1. Due to high degree of SQLite3 backwards compatibility, it is likely that newer versions can work as well.

Required Client Libraries

The SOCI SQLite3 backend uses libsqlite3 client library if available or the built-in version of SQLite3 included in the SOCI source code if this library cannot be found.

Connecting to the Database

To establish a connection to the SQLite3 database, create a Session object using the SQLite3 backend factory together with the database file name:

session sql(sqlite3, "database_filename");

// or:

session sql("sqlite3", "db=db.sqlite timeout=2 shared_cache=true");

The set of parameters used in the connection string for SQLite is:

Boolean options readonly, nocreate, and shared_cache can be either specified without any value, which is equivalent to setting them to 1, or set to one of 1, yes, true or on to enable the option or 0, no, false or off to disable it. Specifying any other value results in an error.

Once you have created a session object as shown above, you can use it to access the database, for example:

int count;
sql << "select count(*) from invoices", into(count);

(See the connection and data binding documentation for general information on using the session class.)

SOCI Feature Support

Dynamic Binding

The SQLite3 backend supports the use of the SOCI row class, which facilitates retrieval of data whose type is not known at compile time.

When calling row::get<T>(), the type you should pass as T depends upon the underlying database type.

For the SQLite3 backend, this type mapping is complicated by the fact the SQLite3 does not enforce [types][INTEGER_PRIMARY_KEY] and makes no attempt to validate the type names used in table creation or alteration statements. SQLite3 will return the type as a string, SOCI will recognize the following strings and match them the corresponding SOCI types:

SQLite3 Data Type SOCI Data Type (data_type) row::get<T> specializations
float, decimal, double, double precision, number, numeric, real dt_double double
int, integer, int2, mediumint, boolean dt_integer int
int8, bigint dt_long_long long long
unsigned big int dt_unsigned_long_long unsigned long long
text, char, character, clob, native character, nchar, nvarchar, varchar, varying character dt_string std::string
date, time, datetime dt_date std::tm
SQLite3 Data Type SOCI Data Type (db_type) row::get<T> specializations
float, decimal, double, double precision, number, numeric, real db_double double
tinyint db_int8 int8_t
smallint db_int16 int16_t
int, integer, int2, mediumint, boolean db_int32 int32_t
int8, bigint db_int64 int64_t
unsigned big int db_uint64 uint64_t
text, char, character, clob, native character, nchar, nvarchar, varchar, varying character db_string std::string
date, time, datetime db_date std::tm

Another consequence of SQLite's lack of type checking is that it is possible to store arbitrarily large integers in a column, even if the type it has been created with wouldn't allow for that. Thus, it is possible that a column of type integer (which should correspond to the possible values of a 32-bit signed integer type) contains a value that overflows a 32-bit integer. In such cases, trying to query the data via row::get<T>, with T being the type as given in the table above, will throw an exception as the selected value would overflow the provided type. You may instead use a T that can holder a wider range (e.g. a 64-bit integer) in order to avoid this exception.

[INTEGER_PRIMARY_KEY] : There is one case where SQLite3 enforces type. If a column is declared as "integer primary key", then SQLite3 uses that as an alias to the internal ROWID column that exists for every table. Only integers are allowed in this column.

(See the dynamic resultset binding documentation for general information on using the row class.)

Binding by Name

In addition to binding by position, the SQLite3 backend supports binding by name, via an overload of the use() function:

int id = 7;
sql << "select name from person where id = :id", use(id, "id")

The backend also supports the SQLite3 native numbered syntax, "one or more literals can be replace by a parameter "?" or ":AAA" or "@AAA" or "$VVV" where AAA is an alphanumeric identifier and VVV is a variable name according to the syntax rules of the TCL programming language." [1]:

int i = 7;
int j = 8;
sql << "insert into t(x, y) values(?, ?)", use(i), use(j);

Bulk Operations

The SQLite3 backend has full support for SOCI's bulk operations interface. However, this support is emulated and is not native.

Transactions

Transactions are also fully supported by the SQLite3 backend.

BLOB Data Type

The SQLite3 backend supports working with data stored in columns of type Blob, via SOCI's BLOB class. Because of SQLite3 general typelessness the column does not have to be declared any particular type.

RowID Data Type

In SQLite3 RowID is an integer. "Each entry in an SQLite table has a unique integer key called the "rowid". The rowid is always available as an undeclared column named ROWID, OID, or ROWID. If the table has a column of type INTEGER PRIMARY KEY then that column is another an alias for the rowid."[2]

Nested Statements

Nested statements are not supported by SQLite3 backend.

Stored Procedures

Stored procedures are not supported by SQLite3 backend

Native API Access

SOCI provides access to underlying datbabase APIs via several get_backend() functions, as described in the beyond SOCI documentation.

The SQLite3 backend provides the following concrete classes for navite API access:

Accessor Function Concrete Class
session_backend* session::get_backend() sqlie3_session_backend
statement_backend* statement::get_backend() sqlite3_statement_backend
rowid_backend* rowid::get_backend() sqlite3_rowid_backend

Backend-specific extensions

SQLite3 result code support

SQLite3 result code is provided via the backend specific sqlite3_soci_error class. Catching the backend specific error allows to retrieve the primary SQL error code using either its result() or extended_result() member functions, corresponding to SQLite primary and extended result codes, e.g.

try {
    sql << "select * from t";
} catch (sqlite3_soci_error const& e) {
    if (e.result() == SQLITE_CONSTRAINT) {
        if (e.extended_result() == SQLITE_CONSTRAINT_DATATYPE) {
            std::cout << "Value is inconsistent with the column type.\n";
        } else {
            std::cout << "Constraint violation detected.\n";
        }
    } else {
        std::cout << "Another SQLite3 error " << e.what() << ", error code: " << e.result() << std::endl;
    }
} catch (soci_error const& e) {
    std::cout << "SOCI error: " << e.what() << std::endl;
}

Note that the extended result can also be retrieved using soci::soci_error::get_backend_error_code() function.

SQLite3 version information

sqlie3_session_backend class, declared in <soci/sqlite3/soci-sqlite3.h>, provides static libversion_number() and libversion() functions which can be used to retrieve the SQLite3 version as a number (e.g. 3049001) and as a string (e.g. 3.49.1) respectively.

Configuration options

None