Every table must have at least one column as the primary index. The data value stored in the columns of the primary index pi is used by teradata to spread the rows among the amps. Every sql table has a primary index, which you define when you set up the table. Types of primary indexes upi and nupi primary indexes define the how the data is distributed for a particular table. The syntax for the create table statement has been changed to permit. Teradata supports industry standard sql to interact with the data stored in tables. If they arent, then the primary index cannot be unique. Instead, it is a mechanism that defines where each data row is physically located on the teradata system.
In teradata we use lot of data dictionary tables dbc to find definitiondetails about anything related to data. Unique primary index are those which has all of its rows as unique. Assume you were joining an employee table with a primary index of empid to a department table with a primary index of deptid. Teradata rdbms sql reference volume 1 fundamentals. Teradata allows up to 64 combined columns to make up the one primary index required for a table. Be large objects lobs have primary key foreign key constraint. Whenever the table needs to be read then each amp has to read portion of the table stored on that amp. If the primary index is not defined, teradata automatically assigns the primary index. Oreilly members get unlimited access to live online training experiences, plus books. Sql merge requests can update or insert into a primaryindexed. Creating teradata database tables using proc sql sas support. The teradata nested join is ideal for oltp workload. Sql fundamentals 3 preface purpose sql fundamentals describes basic teradata sql concepts, including data handling, sql data definition, control, and manipulation, and the sql lexicon. The teradata nested join and the impact of the primary.
We can use teradata qualify row number to have an alternate solution to group by clause or using distinct. Then, the parsing engine uses the hash results to find your data. Say yes to no primary index no pi tables teradata downloads. The first chapter of the teradata indexes book focuses on the primary index pi, as you would probably expect if you knew even a little about teradata, and teradata indexes in particular. This primary index can be different then the primary key and needs to be scripted in the table statement. A column in the column set that defines a partitioned primary index. Repurposing successful database techniques inside teradata. Teradata advance pick topic from this once you are comfortable with teradata basics join strategies merge, nested, hash, product. Teradata sql assistant uses odbc for its connection. So, to rescue and provide the alternative approach, teradata has a feature known as the secondary index. The book has detailed ansi and teradata comparisons, syntax, examples, and tips and tricks learned from the industries top two sql experts. This book includes over examples of all aspects of sql starting at the most basic level and going to the most advanced level with real examples that work and selection from teradata sql book. I would like the below code to pull my previously saved sas data set and join it with an existing sql table in teradata. Usually the primary index is going to be part of the primary key but is not typically the entire primary key.
The hashing algorithm is the means of getting associated rows onto the same amp. Creating teradata database tables using proc sql sas. Partitioning columns do not have to be columns in the primary index. The primary index is used by the hashing algorithm to distribute table rows. The following example creates the salary table with column employeeno as unique primary index. Create table with unique primary index in teradata. The primary index of a table may be defined as either a single column or as multiple columns. It is still only one primary index, but it is merely made up by combining multiple columns together. Book for information about, and usage suggestions for, tables with no primary index. Indexes unique primary index, primary index, unique secondary index, secondary index, partition primary index, aggregate join index. User tables can also be created explicitly without a primary index.
The primary index is defined when the table is created. The unique primary index is considered as a primary key. This is the clause that tells teradata to use a collection of columns in the hash key for each row, and is the most appropriate equivalent to the primary key ddl phrase in oracle and sql server. How do i create a primary index on a teradata table.
Experienced sql users can also see simplified statement, data type, function, and expression descriptions in teradata rdbms sql data dictionary quick reference. Teradata optimizer is one of the matured optimizer in the market. This book is a quick reference for the sql dialect supported by the teradata database. Since the primary index domains are different between the two tables, you can expect the rowstobejoined to be found on different amps.
It has been designed to be parallel since its beginning. Primary index is mandatory for any table in teradata. Each table in teradata is required to have a primary index defined. For information about naming database objects, see sql fundamentals. I would suggest to create a new table w new pi and drop the old one. Basically for getting fast retrieval of data, this is record mended. Creating a partitioned primary index to improve performance. Tradition rdms indexes have nothing to do with teradata s primary index. Teradata allows more than one column to be designated as the primary index. On my project we create teradata database tables via proc sql using the primary index option. In fact, it is by far the most important of all teradata indexes. Adding primary key to a table in teradata forget code.
If any change in primary index needs to be implemented, one needs to drop the table and recreate it. The pi data is converted into the row hash using a mathematical hashing formula. The primary index is very important because the parsing engine needs to hash it. Prerequisites you should be familiar with basic computer technology, the teradata database, and the teradata sql language. Integrates data from a sql compliant database to a teradata database target table using teradata utilities fastload. About this book teradata rdbms sql reference fundamentals iii you should be familiar with basic relational database management technology. Columns that are good candidates for a primary index are ones that will be. Index columnname, characterstring it is common to use the index function in the where clause as well as in the select list. Primary index provides the fastest way to access the data.
Added material to support no primary index nopi tables. Use this book with the other books in the sql book set. It is a field or set of fields which will help the teradata to store records in distributed fashion among the amps. Teradata primary index pi teradata spreads data rows for each table across the amps. The pi will be the primary key of each temporary or target table. Additional indexing options such as primary index, secondary. Candidates should be able to identify use cases of primary, secondary, and join indexes, the impact the primary index has on data distribution, and the differences between primary index and primary key. Paul sinclair and carrie ballinger, teradata columnar, teradata database orange book 549036a02, 2011. You want all of the related data together on the same amp so that cross amp communication is reduced. Primary index considerations in teradata tutorial 12 may. The add primary key function allows the user to add the primary key for the table. We make use of dices view to find any details regrading index. For information about primary index defaults, see teradata vantage database design, b0351094. The parsing engine can quickly hash a primary index and target the requested.
Have secondary indexes usi or nusi have join indexes. As we know, primary indexes are used for the distribution of rows, and sometimes, to reduce the skewness of tables, we might need to choose columns based on even distribution instead of selectivity. In this tutorial, we will create solutions to design indexes to help us improve. Primary index considerations in teradata tutorial 21 may 2020. Nppinon partitioned primary index partitioned primary index on p codeppi data partitioned based on pcode first. The index function is the original teradata function to search for a character string within data.
As you have stated teradata will distribute the data to the amps logical processing units that provide massive parallelism that make td queries run so fast. If the amps start reading at the same time and there are an equal amount of rows on each amp, then parallel processing works best. The teradata primary index is not an index in the traditional sense, as it is not a lookup table. Currently we are not correctly extracting and scripting the primary index information.
As the name suggests, no primary index table means there will be no primary index defined on teradata table. To create a primary index, use the create table statement. Index function in teradata extension in teradata tutorial. Referencing existing sas table in teradata execute. Unique primary index will help the set table to check for duplicates easily rather than comparing entire row under its inspection. While creating a table in teradata, teradata will look for any primary index specified in the ddl. How to find the tables which have ppipartitioned primary index. If the index is not specified, secondly it will look for primary key constraint in ddl for making it primary index. Contrary to what many think, primary indexes do not need to be unique. Columns that are good candidates for a primary index are ones that will be used in joins most frequently. Other than primary index columns if we are using in the where clause, to get fast retrieval data take second index on the columns features. The primary index determines which amp stores an individual row of a table. The teradata nested join and the impact of the primary index.
How to use analytical function as row number with qualify. The teradata primary index is one of the most important tools to ensure highperformance sql queries. Ppiportioned primary index desired to gain proficiency on teradata. Nullable columns are valid for unique indexes teradata database. The main purpose of this feature which allows us to create tables with no primary index in teradata is to improve the performance of fastload and tpump array insert data loading operations. Teradata allows for specifying a primary index in the create table ddl statement. Qualify row number we can use in order to have a specific record or number. Each table in teradata must have at least one column as primary index. Table1,no fallback, no before journal, no after journal, checksum default, default mergeblockratio fieldval integer primary index fieldval. Teradata website teradata youtube tutorial links job titles teradata dba, teradata bi, teradata developer, teradata sql unix professional, senior teradata operations engineer alternatives certifications teradata 14 certified technical specialist teradata 14 certified database administrator teradata 14 certified solutions developer teradata 14 certified enterprise architect teradata 14. After defining the fields use primary index column1, column2 example.
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