TERA Mode For Strings Comparison - NO COLLATE
This section defines the translation specification for string in Tera mode without using COLLATE.
Description
Tera Mode for string comparison and NO COLLATE usages
The Tera Mode string comparison without the use of COLLATE will apply RTRIM
and UPPER
as needed. The default case specification trim behavior may be taken into account.
Sample Source Patterns
Setup data
CREATE TABLE employees (
employee_id INTEGER NOT NULL,
first_name VARCHAR(50) NOT CASESPECIFIC,
last_name VARCHAR(50) CASESPECIFIC,
department VARCHAR(50)
);
INSERT INTO employees(employee_id, first_name, last_name, department) VALUES (1, 'George', 'Snow', 'Sales');
INSERT INTO employees(employee_id, first_name, last_name, department) VALUES (2, 'John', 'SNOW', 'Engineering');
INSERT INTO employees(employee_id, first_name, last_name, department) VALUES (3, 'WIlle', 'SNOW', 'Human resources ');
INSERT INTO employees(employee_id, first_name, last_name, department) VALUES (4, 'Marco', 'SnoW ', 'EngineerinG');
INSERT INTO employees(employee_id, first_name, last_name, department) VALUES (5, 'Mary', ' ', 'SaleS ');
INSERT INTO employees(employee_id, first_name, last_name, department) VALUES (6, 'GEORGE', ' ', 'sales ');
INSERT INTO employees(employee_id, first_name, last_name, department) VALUES (7, 'GEORGE ', ' ', 'salEs ');
INSERT INTO employees(employee_id, first_name, last_name, department) VALUES (8, ' GeorgE ', ' ', 'SalEs ');
INSERT INTO employees (employee_id, first_name, last_name, department) VALUES (9, 'JOHN', ' SnoW', 'IT');
INSERT INTO employees (employee_id, first_name, last_name, department) VALUES (10, 'JOHN ', 'snow', 'Finance ');
CREATE TABLE departments (
department_id INTEGER NOT NULL,
department_name VARCHAR(50) NOT CASESPECIFIC,
location VARCHAR(100) CASESPECIFIC,
PRIMARY KEY (department_id)
);
INSERT INTO departments (department_id, department_name, location) VALUES (101, 'Information Technology', 'New York');
INSERT INTO departments (department_id, department_name, location) VALUES (102, 'Human Resources', 'Chicago');
INSERT INTO departments (department_id, department_name, location) VALUES (103, 'Sales', 'San Francisco');
INSERT INTO departments (department_id, department_name, location) VALUES (104, 'Finance', 'Boston');
Comparison operation
Case 1: Column constraint is NOT CASESPECIFIC and database mode is TERA Mode
This example demonstrates the usage of a column set up as NOT CASESPECIFIC
as it is a first_name
column. Even when asking for the string 'GEorge',
the query execution will retrieve results in Teradata because the case specification is not considered.
To emulate this scenario in Snowflake, there are implemented two functions: RTRIM(UPPER(string_evaluation))
, UPPER
is required in this scenario because the string does not review the case specification.
Teradata
SELECT *
FROM employees
WHERE first_name = 'GEorge ';
Snowflake
SELECT
*
FROM
employees
WHERE
RTRIM(UPPER(first_name)) = RTRIM(UPPER('GEorge '));
Case 2: Column constraint is CASESPECIFIC and database mode is TERA Mode
For this example, the column constraint is CASESPECIFIC
, for which the example does not retrieve rows in Teradata because 'Snow
' is not equal to 'SNOW
'.
In Snowflake, the resulting migration points only to the use of the RTRIM
function since the case specification is important.
Teradata
SELECT *
FROM employees
WHERE last_name = 'SNOW ';
Snowflake
SELECT
*
FROM
employees
WHERE
RTRIM(last_name) = RTRIM('SNOW ');
Case 3: CAST CASESPECIFIC column to NOT CASESPECIFIC and database mode is TERA Mode
Teradata
The (CASESPECIFIC
) overrides the column constraint in the table definition.
SELECT * FROM employees WHERE first_name = 'GEORGE ' (CASESPECIFIC);
Snowflake
SELECT
*
FROM
employees
WHERE
RTRIM(first_name) = RTRIM('GEORGE ' /*** SSC-FDM-TD0032 - CASESPECIFIC CLAUSE WAS REMOVED ***/);
Case 4: CAST NOT CASESPECIFIC column to NOT CASESPECIFIC and database mode is TERA Mode
Teradata
SELECT * FROM employees WHERE first_name = 'GEorge ' (NOT CASESPECIFIC) ;
Snowflake
SELECT
*
FROM
employees
WHERE
UPPER(RTRIM(first_name)) = UPPER(RTRIM('GEorge ' /*** SSC-FDM-TD0032 - NOT CASESPECIFIC CLAUSE WAS REMOVED ***/));
Case 5: Blank spaces case. Column constraint is NOT CASESPECIFIC, database mode is TERA Mode, and using equal operation
Teradata
SELECT *
FROM employees
WHERE last_name = ' ';
Snowflake
SELECT
*
FROM
employees
WHERE
RTRIM(last_name) = RTRIM(' ');
LIKE operation
Case 1: Column constraint is NOT CASESPECIFIC and database mode is TERA Mode
This example is expected to display one row because the case specification is not relevant.
Teradata
SELECT *
FROM employees
WHERE first_name LIKE 'GeorgE';
Snowflake
SELECT *
FROM employees
WHERE first_name ILIKE 'GeorgE';
Case 2: Column constraint is CASESPECIFIC and database mode is TERA Mode
Teradata
SELECT *
FROM employees
WHERE last_name LIKE 'Snow';
Snowflake
SELECT *
FROM employees
WHERE last_name LIKE 'Snow';
Case 3: CAST CASESPECIFIC column to NOT CASESPECIFIC and database mode is TERA Mode
Teradata
SELECT *
FROM employees
WHERE first_name LIKE 'George' (NOT CASESPECIFIC);
Snowflake
SELECT
*
FROM
employees
WHERE
first_name ILIKE 'George' /*** SSC-FDM-TD0032 - NOT CASESPECIFIC CLAUSE WAS REMOVED ***/;
Case 4: CAST NOT CASESPECIFIC column to NOT CASESPECIFIC and database mode is ANSI Mode
Teradata
SELECT *
FROM employees
WHERE first_name LIKE 'GE%' (NOT CASESPECIFIC);
Snowflake
SELECT
*
FROM
employees
WHERE
first_name ILIKE 'GE%' /*** SSC-FDM-TD0032 - NOT CASESPECIFIC CLAUSE WAS REMOVED ***/;
IN Operation
Case 1: Column constraint is NOT CASESPECIFIC and database mode is TERA Mode
Teradata
SELECT *
FROM employees
WHERE first_name IN ('GeorgE');
Snowflake
SELECT *
FROM employees
WHERE RTRIM(UPPER(first_name)) IN (RTRIM(UPPER('GeorgE')));
Case 2: Column constraint is CASESPECIFIC and database mode is TERA Mode
For this example, the usage of the UPPER function is not required since, in the Teradata database, the case specification is relevant to the results.
Teradata
SELECT *
FROM employees
WHERE last_name IN ('SnoW');
Snowflake
SELECT *
FROM employees
WHERE RTRIM(last_name) IN (RTRIM('SnoW'));
ORDER BY clause
Case 1: Column constraint is NOT CASESPECIFIC and database mode is TERA Mode
Notice that this output order can differ.
Teradata
SELECT department
FROM employees
ORDER BY department;
Snowflake
SELECT department
FROM employees
ORDER BY UPPER(department);
Case 2: Column constraint is CASESPECIFIC and database mode is TERA Mode
Notice that this output can differ in order.
Teradata
SELECT last_name
FROM employees
ORDER BY last_name;
Snowflake
SELECT last_name
FROM employees
ORDER BY last_name;
GROUP BY clause
Notice that this output can differ. To ensure a functional equivalence, it is required to use the COLLATE expression.
Please review the SSC-EWI-TD0007 for more information.
The following might be a workaround without collate
:
SELECT RTRIM(UPPER(first_name))
FROM employees
GROUP BY RTRIM(UPPER(first_name));
About the column behavior
Please review the insertion of data in Snowflake. Snowflake does allow the insertion of values as 'GEORGE
' and 'georges
' without showing errors because the case specification is not bound explicitly with the column.
Assume a table and data as follows:
CREATE TABLE students (
first_name VARCHAR(50) NOT CASESPECIFIC
);
INSERT INTO students(first_name) VALUES ('George');
INSERT INTO students(first_name) VALUES (' George');
Notice that this sample does not allow inserting values with upper and lower case letters in the NOT CASESPECIFIC
column because it takes it as the same value. Because the column does not supervise the case specification, the 'GEORGE' and 'george' values are checked as the same information.
The following rows are taken as duplicated row errors:
INSERT INTO students(first_name) VALUES ('GEORGE');
INSERT INTO students(first_name) VALUES ('GeorGe');
INSERT INTO students(first_name) VALUES ('George ');
INSERT INTO students(first_name) VALUES ('GeOrge');
INSERT INTO students(first_name) VALUES ('GEorge');
INSERT INTO students(first_name) VALUES ('George');
Case 1: Column constraint is NOT CASESPECIFIC and database mode is TERA Mode
Teradata
SELECT first_name
FROM employees
GROUP BY first_name;
Snowflake
SELECT
first_name
FROM
employees
!!!RESOLVE EWI!!! /*** SSC-EWI-TD0007 - GROUP BY IS NOT EQUIVALENT IN TERADATA MODE ***/!!!
GROUP BY first_name;
Case 2: Column constraint is CASESPECIFIC and database mode is TERA Mode
Teradata
SELECT last_name
FROM employees
GROUP BY last_name;
Snowflake
SELECT
last_name
FROM
employees
!!!RESOLVE EWI!!! /*** SSC-EWI-TD0007 - GROUP BY IS NOT EQUIVALENT IN TERADATA MODE ***/!!!
GROUP BY last_name;
HAVING clause
The HAVING clause will use the patterns in:
Evaluation operations.
For example:
=, !=, <, >.
LIKE operation.
IN Operation.
CAST to evaluation operation.
CAST to LIKE operation.
The following sample showcases a pattern with evaluation operation.
Sample: Column constraint is CASESPECIFIC and database mode is TERA Mode
Teradata
SELECT last_name
FROM employees
GROUP BY last_name
HAVING last_name = 'Snow';
Snowflake
SELECT last_name
FROM employees
GROUP BY last_name
HAVING RTRIM(last_name) = RTRIM('Snow');
CASE WHEN statement
The CASE WHEN
statement will use the patterns described in:
Evaluation operations.
For example:
=, !=, <, >.
LIKE operation.
IN Operation.
CAST to evaluation operation.
CAST to LIKE operation.
The following sample showcases a pattern with evaluation operation.
Teradata
SELECT first_name,
last_name,
CASE
WHEN department = 'EngineerinG' THEN 'Information Technology'
WHEN last_name = 'SNOW' THEN 'GLOBAL COOL SALES'
ELSE 'Other'
END AS department_full_name
FROM employees;
Snowflake
SELECT
first_name,
last_name,
CASE
WHEN UPPER(RTRIM(department)) = UPPER(RTRIM('EngineerinG'))
THEN 'Information Technology'
WHEN RTRIM(last_name) = RTRIM('SNOW')
THEN 'GLOBAL COOL SALES'
ELSE 'Other'
END AS department_full_name
FROM
employees;
JOIN clause
Simple scenarios are supported.
The JOIN
statement will use the patterns described in:
Evaluation operations.
For example:
=, !=, <, >.
LIKE operation.
IN Operation.
CAST to evaluation operation.
CAST to LIKE operation.
The following sample showcases a pattern with evaluation operation.
Sample: Column constraint is NOT CASESPECIFIC and database mode is TERA Mode
Teradata
SELECT
e.employee_id,
e.first_name,
e.last_name,
d.department_name
FROM
employees e
JOIN
departments d
ON
e.department = d.department_name;
Snowflake
SELECT
e.employee_id,
e.first_name,
e.last_name,
d.department_name
FROM
employees e
JOIN
departments d
ON UPPER(RTRIM(e.department)) = UPPER(RTRIM(d.department_name));
Known Issues
there are some mode-specific SQL statement restrictions:
BEGIN TRANSACTION
,END TRANSACTION
,COMMIT [WORK]
.Data insertion may differ in Snowflake since the case specification is not bound to the column declaration.
GROUP BY
may differ in order, but group the correct values.ORDER BY
behaves differently in Snowflake.If a function has a TRIM() from the source code, this workaround will add the required functions to the source code. So, RTRIM will be applied to the TRIM() source function.
Related EWIs
SSC-EWI-TD0007: GROUP BY IS NOT EQUIVALENT IN TERADATA MODE
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