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Database Management: Tables - page 14 / 35

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1/23/2015  UT Dallas

POEC 6382 Applied GIS Software

14

SELECT and RESELECT

In Tables and INFO, these commands generally must be issued before you can work on tables.

SELECT selects a file (table), and by implication all records within it. Any commands subsequently executed will affect all the records in the table.  You must select a table in Info or Tables before you can work on it. To modify only specific records, use  RESELECT  to create  a subset of records after you have issued SELECT to identify the table.

SELECT <info_file_name>

To clear selected table, issue SELECT without a name (you seldom do this, since normally you simply select another table.)

RESELECT (reduce select, or record select) selects a subset of records from the currently selected data file. (In INFO and Tables, you must have issued SELECT first to select this data file.) Selection criteria are based on logical expressions:

RESELECT {BY | FOR} <logical_expression>

RESELECT FOR ED-YRS LE 4 OR PAY-RATE GT 17.00

ASELECT  adds additional records to the selected set -- requires a logical expression to select additional records.

To clear a selection, use ASELECT without a logical expression to clear selection; in effect, this adds back all records in the file, thus clearing all previous selections.

NSELECT switches the set of selected and unselected records.

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