# MySQL

This driver implements read and write access for spatial data in MySQL tables. This functionality was introduced in GDAL/OGR 1.3.2.

When opening a database, it's name should be specified in the form "MYSQL:dbname[,options]" where the options can include comma seperated items like "user=*userid*", "password=*password*", "host=*host*" and "port=*port*".

As well, a "tables=*table*;*table*..." option can be added to restrict access to a specific list of tables in the database. This option is primarily useful when a database has a lot of tables, and scanning all their schemas would take a significant amount of time.

Currently all regular user tables are assumed to be layers from an OGR point of view, with the table names as the layer names. Named views are not currently supported.

If a single integer field is a primary key, it will be used as the FID otherwise the FID will be assigned sequentially, and fetches by FID will be extremely slow.

By default, SQL statements are passed directly to the MySQL database engine. It's also possible to request the driver to handle SQL commands with OGR SQL engine, by passing "OGRSQL" string to the ExecuteSQL() method, as name of the SQL dialect.

## Caveats

- In the case of a layer defined by a SQL statement, fields either named "OGC_FID" or those that are defined as NOT NULL, are a PRIMARY KEY, and are an integer-like field will be assumed to be the FID.
- Geometry fields are read from MySQL using WKB format. Versions older than 5.0.16 of MySQL are known to have issues with some WKB generation and may not work properly.
- The OGR_FID column, which can be overridden with the MYSQL_FID layer creation option, is implemented as a INT UNIQUE NOT NULL AUTO_INCREMENT field. This appears to implicitly create an index on the field.
- The geometry column, which defaults to SHAPE and can be overridden with the GEOMETRY_NAME layer creation option, is created as a NOT NULL column in unless SPATIAL_INDEX is disabled. By default a spatial index is created at the point the table is created.
- SRS information is stored using the OGC Simple Features for SQL layout, with geometry_columns and spatial_ref_sys metadata tables being created in the specified database if they do not already exist. The spatial_ref_sys table is not pre-populated with SRS and EPSG values like PostGIS. If no EPSG code is found for a given table, the MAX(SRID) value will be used.
- Connection timeouts to the server can be specified with the MYSQL_TIMEOUT environment variable. For example, SET MYSQL_TIMEOUT=3600. It is possible this variable only has an impact when the OS of the MySQL server is Windows.
- The MySQL driver opens a connection to the database using CLIENT_INTERACTIVE mode. You can adjust this setting (interactive_timeout) in your mysql.ini or mysql.cnf file of your server to your liking.
- We are using WKT to insert geometries into the database. If you are inserting big geometries, you will need to be aware of the max_allowed_packet parameter in the MySQL configuration. By default it is set to 1M, but this will not be large enough for really big geometries. If you get an error message like: Got a packet bigger than 'max_allowed_packet' bytes, you will need to increase this parameter.

## Creation Issues

The MySQL driver does not support creation of new datasets (a database within MySQL), but it does allow creation of new layers within an existing database.

By default, the MySQL driver will attempt to preserve the precision of OGR features when creating and reading MySQL layers. For integer fields with a specified width, it will use DECIMAL as the MySQL field type with a specified precision of 0. For real fields, it will use DOUBLE with the specified width and precision. For string fields with a specified width, VARCHAR will be used.

The MySQL driver makes no allowances for character encodings at this time.

The MySQL driver is not transactional at this time.

### Layer Creation Options

- OVERWRITE: This may be "YES" to force an existing layer of the desired name to be destroyed before creating the requested layer.
- LAUNDER: This may be "YES" to force new fields created on this layer to have their field names "laundered" into a form more compatible with MySQL. This converts to lower case and converts some special characters like "-" and "#" to "_". If "NO" exact names are preserved. The default value is "YES".
- PRECISION: This may be "TRUE" to attempt to preserve field widths and precisions for the creation and reading of MySQL layers. The default value is "TRUE".
- MYSQL_GEOM_COLUMN: This option specifies the name of the geometry column. The default value is "SHAPE".
- MYSQL_FID: This option specifies the name of the FID column. The default value is "OGR_FID"
- SPATIAL_INDEX: May be "NO" to stop automatic creation of a spatial index on the geometry column, allowing NULL geometries and possibly faster loading.
- ENGINE: Optionally specify database engine to use. In MySQL 4.x this must be set to MyISAM for spatial tables.

The following example datasource name opens the database schema westholland with password psv9570 for userid root on the port 3306. No hostname is provided, so localhost is assumed. The tables= directive means that only the bedrijven table is scanned and presented as a layer for use.

    MYSQL:westholland,user=root,password=psv9570,port=3306,tables=bedrijven

The following example uses ogr2ogr to create copy the world_borders layer from a shapefile into a MySQL table. It overwrites a table with the existing name borders2, sets a layer creation option to specify the geometry column name to SHAPE2.

    ogr2ogr -f MySQL MySQL:test,user=root world_borders.shp -nln borders2 -update -overwrite -lco GEOMETRY_NAME=SHAPE2

The following example uses ogrinfo to return some summary information about the borders2 layer in the test database.

    ogrinfo MySQL:test,user=root borders2 -so

        Layer name: borders2
        Geometry: Polygon
        Feature Count: 3784
        Extent: (-180.000000, -90.000000) - (180.000000, 83.623596)
        Layer SRS WKT:
        GEOGCS["GCS_WGS_1984",
            DATUM["WGS_1984",
                SPHEROID["WGS_84",6378137,298.257223563]],
            PRIMEM["Greenwich",0],
            UNIT["Degree",0.017453292519943295]]
        FID Column = OGR_FID
        Geometry Column = SHAPE2
        cat: Real (0.0)
        fips_cntry: String (80.0)
        cntry_name: String (80.0)
        area: Real (15.2)
        pop_cntry: Real (15.2)