What is the function of Teradata EXPLAIN Command ?

The Teradata EXPLAIN command can be added to the front of the SQL statement and while execution it gives a detailed analysis for particular statement. The EXPLAIN command can be used to estimate what are the indexes to be used,how much time a query will take and how many rows a query will be return. This command can be used as a useful debug tool to resolve problems with long processing times.

Teradata HELP TABLE Command

The Teradata HELP TABLE command displays the information regarding name, data type, and comment (if applicable), of all columns in particular table:


HELP TABLE Customer_Service.emp;

ColumnName	Type	Comment
emp_number	I	System assigned identification
mgr_emp_number	I
dept_number	I	Department employee works in
job_code	I	Job classification designation
l_name	CF	Employee surname
f_name	CV	Employee given name
hire_date	DA	Date employee was hired
birth_date	DA
sal_amt	D	Annual compensation amount

Data type Representations are as follows:

Type                Description

BF                     BYTE
BV                    VARBYTE

CF                     CHARACTER FIXED

CV                    CHARACTER VARIABLE

DA                    DATE

I1                     BYTEINT

I2                     SMALLINT

AT                     TIME

TS                     TIMESTAMP

D                      DECIMAL

I                       INTEGER

What is BTEQ in Teradata?

It is client s/w that resides on network or channel-attached host. After starting BTEQ,you can log on to Teradata using a TDPid (Teradata Director Program id) with your user id and password. The TDPid identifies the instance of TD you are going to access.

Use of BTEQ (Basic Teradata Query program) is to submit SQL queries to Teradata Database. It works like a interface b/w query and TD.

Teradata SQL basic commands

Teradata basic SQL commands commonly are divided into three categories:

1.Data Definition Language (DDL): - We can define and create database objects such as tables, macros, views, databases and users etc by using DDL commands.

SQL statement	Function
CREATE	To define a table, macro,view, index, trigger or stored procedure.
DROP	To remove a table, view, macro, index, trigger or stored procedure.
ALTER	To change table structure or protection definition.

          

2.Data Manipulation Language (DML): - Work with the data including tasks such as inserting data rows into a table and updating an existing row or performing queries on the data by using the DML  commands. 

SQL statement	Function
SELECT	To select data from one or more tables.
INSERT	To place a new row into a table.
UPDATE	To change data values in one or more existing rows.
DELETE	To remove one or more rows from a table.

3.Data Control Language (DCL): - Here we can perform the administrative tasks such as granting and revoking privileges to database objects or controlling ownership of those objects by using DCL  commands.

SQL statement	Function
GRANT	To give user privileges.
REVOKE	To remove user privileges.
GIVE	To transfer database ownership.

What are set tables and multiset tables in Teradata?

If the table is specified as SET , table do not have duplicate rows.

If the table is specified as MULTISET , table will be having duplicate rows.