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I am using MySQL, I have a table that has 9 columns. One of them is the primary key.
How can I select a single row, by the primary key or column 8 or 4?
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In SQLJ, a single-row query can be executed and its result set data can be retrieved with a single statement: SELECT ... INTO <select target list> . The INTO-clause contains a list of host variables or host expressions that receive the result set data.
To select rows using selection symbols for character or graphic data, use the LIKE keyword in a WHERE clause, and the underscore and percent sign as selection symbols. You can create multiple row conditions, and use the AND, OR, or IN keywords to connect the conditions.
If you want to select only specific columns, replace the * with the names of the columns, separated by commas. The following statement selects just the name_id, firstname and lastname fields from the master_name table.
If I understand your question correctly:
SELECT * FROM tbl WHERE id = 123 OR colname4 = 'x' OR colname8 = 'y' LIMIT 1
The 'LIMIT' keyword makes sure there is only one row returned.
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select *
from MyTable
where MyPrimaryKey = 123
Columns in SQL don't have a defined 'order'. Database systems generally keep track of an order for display purposes, but it doesn't make sense to ask a database to select a column by number. You need to know the column's name in order to query its contents.
The same thing goes for the primary key (which, incidentally, may not be just a single column). You have to know which column it is, and what that column is named, in order to execute a query.
If you don't know these things, or need to figure them out dynamically, then
DESCRIBE tablename;
will tell you the names of each column, and whether it is part of the primary key or not. It will return a table that you can read, like any other result.
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