Retrieving Computed Values
You can retrieve computed values by using arithmetic, string and boolean operators in the
SELECTclause of the statement.
When retrieving computed values, parentheses can be used to force the operation priority.
Without parentheses, the normal precedence rules apply, i.e. first multiplication and division are performed, then addition and subtraction, then comparisons and finally
OR. Operators with the same precedence are evaluated from left to right.
The following computational operators may be used:
See the Mimer SQL Reference Manual, SQL Syntax Elements, for information regarding the type and precision of the result of an arithmetic expression.
Show the exchange rate for the US Dollar if there was a -10% change:SELECT exchange_rate, exchange_rate * 0.90 FROM currencies WHERE code = 'USD';
Evaluating Boolean Expressions
Boolean expressions return a truth value (
FALSE), depending on the result of one or more boolean expressions.
Specify when the exchange rate is less than 1 or the currency code is "ALL":SELECT currency, exchange_rate < 1.0 or code = 'ALL' FROM currencies;
Labels and Computed Values
The computed column is unnamed by default in the result table. A label may be used to provide a name.
For example:SELECT exchange_rate, exchange_rate * 0.90 AS new_exchange_rate FROM currencies WHERE code = 'USD';
A column may also be computed as a constant value, which adds an extra column to the result table.
For example:SELECT exchange_rate, '10% reduction:', exchange_rate * 0.90 AS new_exchange_rate FROM currencies WHERE code = 'USD';
You may also retrieve a value computed using the values in two or more columns, providing that the data types are compatible.
Retrieve the currencies prefixed with the word "Currency:":SELECT 'Currency: ' || currency FROM currencies WHERE code LIKE 'A%';
Padding Concatenated Strings
For string concatenation, column values are padded with trailing blanks to the length of the column definition, if the column data type is fixed-length (
For example:SELECT currency || 'Currency' FROM currencies WHERE code LIKE 'A%';
(If the column data type is variable length, i.e.
NCHAR VARYING, no blank padding is performed.)
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