TABLE CONSTRAINT

Some parts in the output code are omitted for clarity reasons.

Description

Specifies the properties of a PRIMARY KEY, FOREIGN KEY, UNIQUE, or CHECK constraint that is part of a new column definition added to a table by using ALTER TABLE. (https://docs.microsoft.com/en-us/sql/t-sql/statements/alter-table-column-constraint-transact-sql)

Translation for column constraints is relatively straightforward. There are several parts of the syntax that are not required or not supported in Snowflake.

These parts include:

  • CLUSTERED | NONCLUSTERED

  • WITH FILLFACTOR = fillfactor

  • WITH ( index_option [, ...n ] )

  • ON { partition_scheme_name ( partition_column_name ) | filegroup | "default" }

  • NOT FOR REPLICATION

  • CHECK [ NOT FOR REPLICATION ]

Syntax in SQL Server

[ CONSTRAINT constraint_name ]   
{   
    { PRIMARY KEY | UNIQUE }   
        [ CLUSTERED | NONCLUSTERED ]   
        (column [ ASC | DESC ] [ ,...n ] )  
        [ WITH FILLFACTOR = fillfactor   
        [ WITH ( <index_option>[ , ...n ] ) ]  
        [ ON { partition_scheme_name ( partition_column_name ... )  
          | filegroup | "default" } ]   
    | FOREIGN KEY   
        ( column [ ,...n ] )  
        REFERENCES referenced_table_name [ ( ref_column [ ,...n ] ) ]   
        [ ON DELETE { NO ACTION | CASCADE | SET NULL | SET DEFAULT } ]   
        [ ON UPDATE { NO ACTION | CASCADE | SET NULL | SET DEFAULT } ]   
        [ NOT FOR REPLICATION ]   
    | CONNECTION
        ( { node_table TO node_table } 
          [ , {node_table TO node_table }]
          [ , ...n ]
        )
        [ ON DELETE { NO ACTION | CASCADE } ]
    | DEFAULT constant_expression FOR column [ WITH VALUES ]   
    | CHECK [ NOT FOR REPLICATION ] ( logical_expression )  
}

Syntax in Snowflake

inlineUniquePK ::=
  [ CONSTRAINT <constraint_name> ]
  { UNIQUE | PRIMARY KEY }
  [ [ NOT ] ENFORCED ]
  [ [ NOT ] DEFERRABLE ]
  [ INITIALLY { DEFERRED | IMMEDIATE } ]
  [ ENABLE | DISABLE ]
  [ VALIDATE | NOVALIDATE ]
  [ RELY | NORELY ]
[ CONSTRAINT <constraint_name> ]
  { UNIQUE | PRIMARY KEY }
  [ [ NOT ] ENFORCED ]
  [ [ NOT ] DEFERRABLE ]
  [ INITIALLY { DEFERRED | IMMEDIATE } ]
  [ ENABLE | DISABLE ]
  [ VALIDATE | NOVALIDATE ]
  [ RELY | NORELY ]

Sample Source Patterns

Multiple ALTER TABLE instances

SQL Server

IN -> SqlServer_01.sql
-- PRIMARY KEY
ALTER TABLE
    [Person]
ADD
    CONSTRAINT [PK_EmailAddress_BusinessEntityID_EmailAddressID] PRIMARY KEY CLUSTERED (
        [BusinessEntityID] ASC,
        [EmailAddressID] ASC
    ) ON [PRIMARY]
GO

-- FOREING KEY TO ANOTHER TABLE
ALTER TABLE
    [Person].[EmailAddress] WITH CHECK
ADD
    CONSTRAINT [FK_EmailAddress_Person_BusinessEntityID] FOREIGN KEY([BusinessEntityID]) REFERENCES [Person].[Person] ([BusinessEntityID]) ON DELETE CASCADE
GO

Snowflake

OUT -> SqlServer_01.sql
-- PRIMARY KEY
ALTER TABLE Person
ADD
    CONSTRAINT PK_EmailAddress_BusinessEntityID_EmailAddressID PRIMARY KEY
                                                                           !!!RESOLVE EWI!!! /*** SSC-EWI-0040 - THE STATEMENT IS NOT SUPPORTED IN SNOWFLAKE ***/!!! CLUSTERED (BusinessEntityID, EmailAddressID);

-- FOREING KEY TO ANOTHER TABLE
ALTER TABLE Person.EmailAddress
----** SSC-FDM-0014 - CHECK STATEMENT NOT SUPPORTED **
--WITH CHECK
ADD
    CONSTRAINT FK_EmailAddress_Person_BusinessEntityID FOREIGN KEY(BusinessEntityID) REFERENCES Person.Person (BusinessEntityID) ON DELETE CASCADE ;

DEFAULT within constraints

SQL Server

IN -> SqlServer_02.sql
CREATE TABLE Table1
(
   COL_VARCHAR VARCHAR,
   COL_INT INT,
   COL_DATE DATE
);

ALTER TABLE
    Table1
ADD
    CONSTRAINT [DF_Table1_COL_INT] DEFAULT ((0)) FOR [COL_INT]
GO

ALTER TABLE
    Table1
ADD
    COL_NEWCOLUMN VARCHAR,
    CONSTRAINT [DF_Table1_COL_VARCHAR] DEFAULT ('NOT DEFINED') FOR [COL_VARCHAR]
GO

ALTER TABLE
    Table1
ADD
    CONSTRAINT [DF_Table1_COL_DATE] DEFAULT (getdate()) FOR [COL_DATE]    
GO

Snowflake

OUT -> SqlServer_02.sql
CREATE OR REPLACE TABLE Table1 (
   COL_VARCHAR VARCHAR DEFAULT ('NOT DEFINED'),
   COL_INT INT DEFAULT ((0)),
   COL_DATE DATE DEFAULT (CURRENT_TIMESTAMP() :: TIMESTAMP)
)
COMMENT = '{"origin":"sf_sc","name":"snowconvert","version":{"major":1, "minor":0},"attributes":{"component":"transact"}}'
;

----** SSC-FDM-TS0020 - DEFAULT CONSTRAINT MAY HAVE BEEN ADDED TO TABLE DEFINITION **

--ALTER TABLE Table1
--ADD
--    CONSTRAINT DF_Table1_COL_INT DEFAULT ((0)) FOR COL_INT
                                                          ;

ALTER TABLE Table1
ADD COL_NEWCOLUMN VARCHAR;

----** SSC-FDM-TS0020 - DEFAULT CONSTRAINT MAY HAVE BEEN ADDED TO TABLE DEFINITION **

--ALTER TABLE Table1
--ADD
--CONSTRAINT DF_Table1_COL_VARCHAR DEFAULT ('NOT DEFINED') FOR COL_VARCHAR
                                                                        ;

----** SSC-FDM-TS0020 - DEFAULT CONSTRAINT MAY HAVE BEEN ADDED TO TABLE DEFINITION **