Check constraint in appian MYSQL database

CHECK constraint - if you have access to the database directly I don't see why you could not apply CHECK constraints where you would like, but note I am not a MySQL expert.

Additionally, you can certainly update values in a table column based on another.  Utilize a!queryEntity() to retrieve data into your CDT, manipulate the CDT as needed, then Write to Datastore back to the DB.  More details on your use case might be helpful here however.  

CHECK constraint - if you have access to the database directly I don't see why you could not apply CHECK constraints where you would like, but note I am not a MySQL expert.

Additionally, you can certainly update values in a table column based on another.  Utilize a!queryEntity() to retrieve data into your CDT, manipulate the CDT as needed, then Write to Datastore back to the DB.  More details on your use case might be helpful here however.  

Hi,

         I just find appian cloud - database  cannot  add check constraint by sql. It always remind me  

       "  A new statement was found, but no delimiter between it and the previous one. (near "check" at position 84 )"

So I want to know Whether can I use the check order to complete my constraint.

xug0001 

You will get this error, when the table already has some data and fails to qualify the check constraint requirements. Try to fix the data first and then create the check constraint.

I was able to re-produce the issue by following the scripts below

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    City varchar(255),
    PRIMARY Key (ID)
);

INSERT INTO `Persons` (`ID`, `LastName`, `FirstName`, `Age`, `City`) VALUES ('10', 'Test', 'Test', '17', 'Test');

ALTER TABLE Persons ADD CONSTRAINT CHK_PersonAge CHECK (Age>=18); 
-- This will throw the error message as you mentioned


-- Fix the data by using the blow query and create check constraint
UPDATE `Persons` SET `Age` = '18' WHERE `Persons`.`ID` = 10;
ALTER TABLE Persons ADD CONSTRAINT CHK_PersonAge CHECK (Age>=18); 

Thank you for your reply. However I still can not add check constraint even I make sure all data is fit to my check condition. Like this.

It looks like the key 'check' is illegal on APPIAN cloud database. Because it remind me I need a delimiter in appian rule. It means the key word 'CHECK' can only be used at the first word in a sql. 

your script is exactly right. I can easily run the constraint SQL in other tools .

I had solved this question in another way. By creating a trigger to validation before insert.

Thank you so much. 

We typically implement this kind of checks in the application or UI layer. Not in DB.