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| === Declaring Databases for Raw Data Files === | === Declaring Databases for Raw Data Files === | ||
| - | Databases in Omnidex are of a particular type, such as Oracle, SQL Server, MySQL or ODBC. A database that accesses raw data file has its own type: FILE. All tables within this database must be raw data files, though they can be a mixture of the types of raw data files supported by Omnidex. | + | Databases in Omnidex are of a particular type, such as Oracle, SQL Server, MySQL or ODBC. A database that accesses raw data files has its own type: FILE. All tables within this database must be raw data files, though they can be a mixture of the types of raw data files supported by Omnidex. |
| <code> | <code> | ||
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| Tables will point to one or more fixed-length files, and the files must match the record layout specified in the [[dev:sql:statements:create_table:home|CREATE TABLE]] statement. In the CREATE TABLE statement, the PHYSICAL clause is used to point to the physical location of the raw data file. This PHYSICAL clause can contain a relative path name (relative to the location of the Omnidex Environment File) such as "dat/states.dat", or an absolute path name such as "d:/class/lab1/dat/states.dat". This PHYSICAL clause can also contain wildcards as described below, and can also reference [[appendix:reference:envvar:home|environment variables]] using special syntax. | Tables will point to one or more fixed-length files, and the files must match the record layout specified in the [[dev:sql:statements:create_table:home|CREATE TABLE]] statement. In the CREATE TABLE statement, the PHYSICAL clause is used to point to the physical location of the raw data file. This PHYSICAL clause can contain a relative path name (relative to the location of the Omnidex Environment File) such as "dat/states.dat", or an absolute path name such as "d:/class/lab1/dat/states.dat". This PHYSICAL clause can also contain wildcards as described below, and can also reference [[appendix:reference:envvar:home|environment variables]] using special syntax. | ||
| - | <code sql> | + | <code> |
| create table "STATES" | create table "STATES" | ||
| physical "dat/states.dat" | physical "dat/states.dat" | ||
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| In the example above, a single file was used as the source of data for a table. It is also possible for multiple files to be used as the source of data for a table. As long as the files all share the same record layout, they will all be processed when reading the table. Filesets can be declared as a comma-separated list of files, or they can be declared using wildcards in the filename. In this example, three files are declared individually in the PHYSICAL clause: | In the example above, a single file was used as the source of data for a table. It is also possible for multiple files to be used as the source of data for a table. As long as the files all share the same record layout, they will all be processed when reading the table. Filesets can be declared as a comma-separated list of files, or they can be declared using wildcards in the filename. In this example, three files are declared individually in the PHYSICAL clause: | ||
| - | <code sql> | + | <code> |
| create table "STATES" | create table "STATES" | ||
| physical "c:/class/lab1/dat/states1.dat, | physical "c:/class/lab1/dat/states1.dat, | ||
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| In this second example, wildcards are used to declare these files: | In this second example, wildcards are used to declare these files: | ||
| - | <code sql> | + | <code> |
| create table "STATES" | create table "STATES" | ||
| physical "c:/class/lab1/dat/states*.dat, | physical "c:/class/lab1/dat/states*.dat, | ||
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| Files can reside in multiple directories and in multiple drives or volumes to allow a table to span multiple storage devices. Files may also reside on a Storage Area Network (SAN); in fact, this is one of the most common implementations of Omnidex. Files may also reside on Microsoft Windows mapped drives; however, users should expect performance degradation to occur in this scenario. | Files can reside in multiple directories and in multiple drives or volumes to allow a table to span multiple storage devices. Files may also reside on a Storage Area Network (SAN); in fact, this is one of the most common implementations of Omnidex. Files may also reside on Microsoft Windows mapped drives; however, users should expect performance degradation to occur in this scenario. | ||
| - | Wildcards provide a great flexibility since they allow more data to be added to a table by simply moving another file into place. Care should be taken with this approach, though, since the table must be reindexed as soon as new data is in place. | + | Wildcards provide great flexibility since they allow more data to be added to a table by simply moving another file into place. Care should be taken with this approach, though, since the table must be reindexed as soon as new data is in place. |