How do I see constraints on a table in Teradata?
Columns
- DatabaseName – name of constraint database.
- TableName – name of the table constraint is on.
- ConstraintLevel – ‘Table’ if constraint is table-level constraint,
- ConstraintName – name of constraint for table-level constraints and name of column for column-level constraint:
- Text – full constraint definition.
What are the table level constraints?
Table-level constraints refer to one or more columns in the table. Table-level constraints specify the names of the columns to which they apply. Table-level CHECK constraints can refer to 0 or more columns in the table.
What are the constraints in Teradata?
Teradata has some fundamental rules about constraints:
- Always name table level constraints.
- Constraint names can be up to 30 characters.
- Constraint names must be unique among all other constraint names defined for a table.
- Constraints can be specified at the column or table level.
Where is primary key in Teradata table?
If you explicitly define a primary key in the table definition, teradata will maintain it with indextype = ‘K’ in the DBC. Indices view. Otherwise you are stuck to looking for unique indexes via uniquenessflag = ‘y’ in dbc. indices ( club on the index number for composite indexes) …
Which constraint Cannot be on table level?
Why Null Constraint cannot be used at table level.
Is PRIMARY KEY a table level constraint?
Syntax. PRIMARY KEY constraints can be defined at the table level.
How do I drop a constraint in Teradata?
You can drop a constraint in a table by specifying the name of the constraint. Syntax: ALTER TABLE tbl_name DROP CONSTRAINT constraint_name.
What are constraints in SQL table?
SQL constraints are used to specify rules for the data in a table. Constraints are used to limit the type of data that can go into a table. This ensures the accuracy and reliability of the data in the table. If there is any violation between the constraint and the data action, the action is aborted.
What is the difference between primary index and primary key?
The primary index contains the key fields of the table and a pointer to the non-key fields of the table. The primary index is created automatically when the table is created in the database. Primary key is mandatory.it avoid the duplicate of data.
Can primary key be null in Teradata?
15.00 – 5516 PRIMARY KEY or UNIQUE column(s) must be NOT NULL. – Teradata Database.
Which constraint Cannot be defined at table level?
Columns that you specify as unique or that you use as part of a table-level unique constraint cannot be nullable.
What is the difference between primary key and primary index in Teradata?
The Primary Index distributes the data, and the Primary Key uniquely identifies an object. The primary Key and Primary Index are often the same because the Primary Key is unique by definition. Therefore, when used as a Primary Index ensures that the rows of a table are distributed evenly across all AMPs.
Can we drop primary index in Teradata?
You cannot alter a PI in teradata unless the table is empty. You will need to copy the data out to another table, volatile or permanent. Show activity on this post. in general you should not change the PI on Teradata.
Which of the following Cannot be defined as table level constraints?
Can primary index have duplicates in Teradata?
Teradata Database Introduction to Teradata. You can create a table with a Unique Primary Index (UPI), a Non-Unique Primary Index (NUPI), or No Primary Index (NoPI). the PI is a column, or columns, that may have duplicate values.
Why do we use secondary index in Teradata?
Secondary indexes are never required for Teradata Database tables, but they can often improve system performance. A Secondary Index (SI) is an alternate data access path. It allows accessing the data without having to do a full-table scan.
What is Pi in Teradata?
Primary index is used to specify where the data resides in Teradata. It is used to specify which AMP gets the data row. Each table in Teradata is required to have a primary index defined. If the primary index is not defined, Teradata automatically assigns the primary index.