Calculated Fields

Download this document

Calculated fields allow dynamically defining new columns in queries using expressions, without modifying TM/QM models.

1. Overview

There are two ways to define calculated fields:

1. calculatedFields parameter: Defined in DSL requests
2. Inline expressions: Directly write expression as alias in columns

---

2. Define via calculatedFields

2.1 Basic Format

{
    "param": {
        "calculatedFields": [
            {
                "name": "netAmount",
                "caption": "Net Sales Amount",
                "expression": "salesAmount - discountAmount"
            }
        ],
        "columns": ["orderId", "salesAmount", "discountAmount", "netAmount"]
    }
}

2.2 Field Description

Field	Type	Required	Description
name	string	Yes	Field name, referenced in columns/slice/orderBy
caption	string	No	Display name
expression	string	Yes	Calculation expression
description	string	No	Field description
agg	string	No	Aggregation type (for autoGroupBy scenarios)

2.3 Column References in Expressions

Expressions can reference:

• Property names in the model
• Measure names in the model
• Dimension columns: dimension$caption, dimension$id, dimension$property
• Other calculated field names (must be defined before current field)

---

3. Define via Inline Expressions

Use expression as alias format directly in columns:

{
    "param": {
        "columns": [
            "orderId",
            "salesAmount",
            "salesAmount * 1.1 as adjustedAmount",
            "ROUND(salesAmount, 2) as roundedAmount"
        ]
    }
}

3.1 Aggregation Expressions

{
    "param": {
        "columns": [
            "product$categoryName",
            "sum(salesAmount) as totalSales",
            "count(*) as orderCount"
        ],
        "groupBy": [
            { "field": "product$categoryName" }
        ]
    }
}

Note: Inline expression aliases cannot conflict with existing field names in the model, otherwise an error will be thrown.

---

4. Supported Expressions

4.1 Arithmetic Operations

Operator	Description	Example
+	Addition	salesAmount + taxAmount
-	Subtraction	salesAmount - discountAmount
*	Multiplication	unitPrice * quantity
/	Division	profitAmount / salesAmount
%	Modulo	quantity % 10

Compound Expressions:

(salesAmount - discountAmount) * 1.13

4.2 Math Functions

Function	Description	Example
ABS(x)	Absolute value	ABS(discountAmount)
ROUND(x, n)	Rounding	ROUND(salesAmount, 2)
CEIL(x)	Ceiling	CEIL(quantity / 10)
FLOOR(x)	Floor	FLOOR(quantity / 10)
MOD(x, y)	Modulo	MOD(quantity, 10)
POWER(x, y)	Power	POWER(2, 3)
SQRT(x)	Square root	SQRT(variance)

4.3 Date Functions

Function	Description	Example
YEAR(date)	Extract year	YEAR(salesDate$caption)
MONTH(date)	Extract month	MONTH(salesDate$caption)
DAY(date)	Extract day	DAY(salesDate$caption)
DATE(datetime)	Extract date part	DATE(orderTime)
NOW()	Current time	NOW()
DATE_ADD(date, interval)	Date addition	DATE_ADD(orderDate, 7)
DATE_SUB(date, interval)	Date subtraction	DATE_SUB(orderDate, 7)
DATEDIFF(d1, d2)	Date difference	DATEDIFF(NOW(), orderDate)

4.4 String Functions

Function	Description	Example
CONCAT(a, b, ...)	String concatenation	CONCAT(orderId, '-', orderLineNo)
SUBSTRING(s, start, len)	Substring	SUBSTRING(orderId, 1, 4)
UPPER(s)	Uppercase	UPPER(status)
LOWER(s)	Lowercase	LOWER(email)
TRIM(s)	Trim spaces	TRIM(customerName)
LENGTH(s)	String length	LENGTH(productName)

4.5 Null Handling Functions

Function	Description	Example
COALESCE(a, b, ...)	Return first non-null value	COALESCE(discountAmount, 0)
NULLIF(a, b)	Return NULL if equal	NULLIF(status, 'UNKNOWN')
IFNULL(a, b)	Return default if null	IFNULL(discountAmount, 0)

4.6 Aggregation Functions

Function	Description	Example
SUM(x)	Sum	SUM(salesAmount)
AVG(x)	Average	AVG(unitPrice)
COUNT(*)	Count	COUNT(*)
MAX(x)	Maximum	MAX(salesAmount)
MIN(x)	Minimum	MIN(salesAmount)

---

5. Complete Examples

5.1 Simple Arithmetic Expression

{
    "param": {
        "calculatedFields": [
            {
                "name": "netAmount",
                "caption": "Net Sales Amount",
                "expression": "salesAmount - discountAmount"
            }
        ],
        "columns": ["orderId", "salesAmount", "discountAmount", "netAmount"]
    }
}

Generated SQL:

SELECT
    order_id AS orderId,
    sales_amount AS salesAmount,
    discount_amount AS discountAmount,
    (sales_amount - discount_amount) AS netAmount
FROM fact_sales

5.2 Profit Rate Calculation

{
    "param": {
        "calculatedFields": [
            {
                "name": "profitRate",
                "caption": "Profit Rate (%)",
                "expression": "profitAmount * 100.0 / salesAmount"
            }
        ],
        "columns": ["orderId", "salesAmount", "profitAmount", "profitRate"],
        "slice": [
            { "field": "salesAmount", "op": ">", "value": 0 }
        ]
    }
}

5.3 Chained Calculated Fields

Calculated fields can reference other calculated fields:

{
    "param": {
        "calculatedFields": [
            {
                "name": "netAmount",
                "caption": "Net Sales Amount",
                "expression": "salesAmount - discountAmount"
            },
            {
                "name": "taxIncluded",
                "caption": "Tax Included Amount",
                "expression": "netAmount * 1.13"
            }
        ],
        "columns": ["orderId", "salesAmount", "netAmount", "taxIncluded"]
    }
}

5.4 Reference Dimension Columns

{
    "param": {
        "calculatedFields": [
            {
                "name": "yearMonth",
                "caption": "Year-Month",
                "expression": "CONCAT(YEAR(salesDate$caption), '-', MONTH(salesDate$caption))"
            }
        ],
        "columns": ["orderId", "salesDate$caption", "yearMonth", "salesAmount"]
    }
}

5.5 Calculated Field as Filter Condition

{
    "param": {
        "calculatedFields": [
            {
                "name": "profitRate",
                "caption": "Profit Rate",
                "expression": "profitAmount * 100.0 / salesAmount"
            }
        ],
        "columns": ["orderId", "salesAmount", "profitAmount", "profitRate"],
        "slice": [
            { "field": "salesAmount", "op": ">", "value": 0 },
            { "field": "profitRate", "op": ">", "value": 10 }
        ]
    }
}

5.6 Calculated Fields in Grouped Aggregations

{
    "param": {
        "columns": [
            "product$categoryName",
            "sum(salesAmount) as totalSales",
            "sum(profitAmount) as totalProfit",
            "sum(profitAmount) * 100.0 / sum(salesAmount) as profitRate"
        ],
        "groupBy": [
            { "field": "product$categoryName" }
        ],
        "orderBy": [
            { "field": "totalSales", "order": "desc" }
        ]
    }
}

---

6. Security

6.1 Prohibited Functions

The following functions will be intercepted and throw SecurityException:

• EXEC, EXECUTE
• DROP, DELETE, UPDATE, INSERT
• CREATE, ALTER, TRUNCATE
• Other functions not in the whitelist

6.2 Error Handling

Error Type	Description
Reference non-existent column	Throws exception indicating column doesn't exist
Duplicate calculated field name	Throws exception indicating name already exists
Alias conflicts with existing field	Throws exception indicating field name conflict
Using prohibited function	Throws SecurityException

---

7. Best Practices

1. Avoid division by zero: Add salesAmount > 0 condition before division
2. Use COALESCE: Handle fields that may be NULL
3. Naming conventions: Use meaningful names for calculated fields, avoid conflicts with existing fields
4. Chain dependencies: Referenced calculated fields must be defined before the referencing field
5. Performance considerations: Complex calculated fields may impact query performance

---

Next Steps

• JSON Query DSL - Complete DSL query syntax (recommended)
• Query API - HTTP API reference
• TM Syntax Manual - Table model definitions
• QM Syntax Manual - Query model definitions