 ## Retrieving Computed Values

You can retrieve computed values by using arithmetic and string operators in the `SELECT` clause of the statement.

When retrieving computed values, parentheses can be used to force the operation priority.

Without parentheses, the normal precedence rules for arithmetic apply, i.e. multiplication and division are performed before addition and subtraction, and operators with the same precedence are evaluated from left to right.

The following computational operators may be used:

##### Explanation
``` +
```
``` -
```
subtraction
``` *
```
multiplication
``` /
```
division
``` ||
```
string concatenation

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';
```
##### Returns:

EXCHANGE_RATE
``` 0.8711
```
``` 0.783990
```

### 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';
```
##### Returns:

EXCHANGE_RATE
NEW_EXCHANGE_RATE
0.8711
0.783990

### Constant Values

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';
```
##### Returns:

EXCHANGE_RATE
```
```
NEW_EXCHANGE_RATE
0.8711
``` 10% reduction:
```
0.783990

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%';
```
##### Returns:

```
```
``` Currency: UAE Dirhams
```
``` Currency: Afghanis
```
``` Currency: Leke
```
``` Currency: Armenian Drams
```
``` Currency: Netherlands Antillian Guilders
```
``` Currency: Kwanza
```
``` ...
```

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 (`CHARACTER` or `NATIONAL CHARACTER`).

##### For example:
``` SELECT currency || 'Currency'
FROM currencies
WHERE code LIKE 'A%';
```
##### Returns:

```
```
``` UAE Dirhams                      Currency
```
``` Afghanis                         Currency
```
``` Leke                             Currency
```
``` Armenian Drams                   Currency
```
``` Netherlands Antillian Guilders   Currency
```
``` Kwanza                           Currency
```
``` ...
```

(If the column data type is variable length, i.e. `VARCHAR` or `NCHAR VARYING`, no blank padding is performed.) Mimer Information Technology AB Voice: +46 18 780 92 00 Fax: +46 18 780 92 40 info@mimer.se