Generating Primary Keys For Redshift

Posted : admin On 14.04.2020

Sql Primary Keys
Secondary Keys
Generating Primary Keys For Redshift 2017
Redshift Primary Key Constraint

Duplicate Record Delete Query Generator For Amazon Redshift

delete_dup_records_redshift.rb

# Duplicate record delete query generator for Amazon Redshift

# By running a generated query, duplicate rows in a specified table will be removed.

# Usage:

# ruby delete_dup_records_redshift.rb <table-name> <priary-keys-with-comma-separator>

unlessARGV.count2

puts<<EOT

Usage:

ruby delete_dup_records_redshift.rb <table name> <primary keys>

Example:

# Single primary key

ruby delete_dup_records_redshift.rb users id

# Composite primary keys

ruby delete_dup_records_redshift.rb users_groups user_id,group_id

# Specify schema name

ruby delete_dup_records_redshift.rb public.users id

EOT

exit1

end

table=ARGV[0]# ex: 'm_test_table_multi_pk'

primary_keys=ARGV[1].split(',')# ex: 'id1,id2'

temp_table='#{table}_temp_for_dup_rows_#{Time.now.strftime('%Y%m%d_%H%M%S')}'

#### Main

QUERY_TMPL=<<EOT

-- Check duplicate row count

SELECT '%{table}' as table, count(*) as num_dup_keys FROM (SELECT %{primary_keys} FROM %{table} GROUP BY %{primary_keys} HAVING count(*) <> 1);

-- Delete duplicate rows

BEGIN;

LOCK %{table};

SELECT count(*) FROM (SELECT %{primary_keys} FROM %{table} GROUP BY %{primary_keys} HAVING count(*) <> 1);

CREATE TABLE %{temp_table} (LIKE %{table});

INSERT INTO %{temp_table} (SELECT distinct a.* FROM %{table} a, (SELECT %{primary_keys} FROM %{table} GROUP BY %{primary_keys} HAVING count(*) <> 1) b where %{insert_condition} );

DELETE FROM %{table} using %{temp_table} where %{delete_condition};

INSERT INTO %{table} (select * from %{temp_table});

DROP TABLE %{temp_table};

END;

EOT

putsQUERY_TMPL % {

table: table,

temp_table: temp_table,

primary_keys: primary_keys.join(','),

insert_condition: primary_keys.collect{pk'a.#{pk} = b.#{pk}'}.join(' AND '),

delete_condition: primary_keys.collect{pk'#{table}.#{pk} = #{temp_table}.#{pk}'}.join(' AND '),

}

Looker expects that each view defines exactly one dimension with the primarykey parameter and that there are no duplicate values for a primary key field within a table. If this constraint is not respected, aggregates across joins can get counted two or more times, leading to unusually large numbers. Amazon Redshift’s DISTKEY and SORTKEY are a powerful set of tools for optimizing query performance. Because Redshift is a columnar database with compressed storage, it doesn’t use indexes that way a transactional database such as MySQL or PostgreSQL would. Instead, it uses DISTKEYs and SORTKEYs. Mar 25, 2016 I think that some databases let you use functions in the definition of indices or primary keys, such as a primary key defined over a suffix of a string column, but I imagine that it's a less-common use-case and I don't think that Redshift supports it. Therefore, having a column metadata field called 'primarykey' might be sufficient. Feb 09, 2015 In my current work we are migrating some of our workload to Redshift. And that includes migrating many of tables from Oracle to Amazon Redshift. We know these two are very different platforms and we cant simply copy the Oracle's DDL and create a table on Redshift. Redshift doesn't(yet) enforce primary keys, the data types. The first is PRIMARY KEY, which as the name suggests, forces the specified column to behave as a completely unique index for the table, allowing for rapid searching and queries. While SQL Server only allows one PRIMARY KEY constraint assigned to a single table, that PRIMARY KEY can be defined for more than one column.

Oct 12, 2014 Most of the cases an auto increment identity column is considered as the primary key of the table. It is also widely used as a surrogate key of dimension tables in a typical data warehouse system. Identity column SEED-STEP are used to generate.

examples.txt

# Single primary key

$ ruby delete_dup_records_redshift.rb m_test_table id

-- Check duplicate row count

SELECT 'm_test_table' as table, count(*) as num_dup_keys FROM (SELECT id FROM m_test_table GROUP BY id HAVING count(*) <> 1);

-- Delete duplicate rows

BEGIN;

LOCK m_test_table;

SELECT count(*) FROM (SELECT id FROM m_test_table GROUP BY id HAVING count(*) <> 1);

CREATE TABLE m_test_table_temp_for_dup_rows_20160315_153707 (LIKE m_test_table);

INSERT INTO m_test_table_temp_for_dup_rows_20160315_153707 (SELECT distinct a.* FROM m_test_table a, (SELECT id FROM m_test_table GROUP BY id HAVING count(*) <> 1) b where a.id = b.id );

DELETE FROM m_test_table using m_test_table_temp_for_dup_rows_20160315_153707 where m_test_table.id = m_test_table_temp_for_dup_rows_20160315_153707.id;

INSERT INTO m_test_table (select * from m_test_table_temp_for_dup_rows_20160315_153707);

DROP TABLE m_test_table_temp_for_dup_rows_20160315_153707;

END;

# Composite primary keys

$ ruby delete_dup_records_redshift.rb m_test_table_multi_pk id1,id2

-- Check duplicate row count

SELECT 'm_test_table_multi_pk' as table, count(*) as num_dup_keys FROM (SELECT id1,id2 FROM m_test_table_multi_pk GROUP BY id1,id2 HAVING count(*) <> 1);

-- Delete duplicate rows

BEGIN;

LOCK m_test_table_multi_pk;

SELECT count(*) FROM (SELECT id1,id2 FROM m_test_table_multi_pk GROUP BY id1,id2 HAVING count(*) <> 1);

CREATE TABLE m_test_table_multi_pk_temp_for_dup_rows_20160315_153607 (LIKE m_test_table_multi_pk);

INSERT INTO m_test_table_multi_pk_temp_for_dup_rows_20160315_153607 (SELECT distinct a.* FROM m_test_table_multi_pk a, (SELECT id1,id2 FROM m_test_table_multi_pk GROUP BY id1,id2 HAVING count(*) <> 1) b where a.id1 = b.id1 AND a.id2 = b.id2 );

DELETE FROM m_test_table_multi_pk using m_test_table_multi_pk_temp_for_dup_rows_20160315_153607 where m_test_table_multi_pk.id1 = m_test_table_multi_pk_temp_for_dup_rows_20160315_153607.id1 AND m_test_table_multi_pk.id2 = m_test_table_multi_pk_temp_for_dup_rows_20160315_153607.id2;

INSERT INTO m_test_table_multi_pk (select * from m_test_table_multi_pk_temp_for_dup_rows_20160315_153607);

DROP TABLE m_test_table_multi_pk_temp_for_dup_rows_20160315_153607;

END;

AUTO INCREMENT Field

Auto-increment allows a unique number to be generated automatically when a new record is inserted into a table.

Often this is the primary key field that we would like to be created automatically every time a new record is inserted.

Syntax for MySQL

The following SQL statement defines the 'Personid' column to be an auto-increment primary key field in the 'Persons' table:

CREATE TABLE Persons (
Personid int NOT NULL AUTO_INCREMENT,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Age int,
PRIMARY KEY (Personid)
);

MySQL uses the AUTO_INCREMENT keyword to perform an auto-increment feature.

By default, the starting value for AUTO_INCREMENT is 1, and it will increment by 1 for each new record.

To let the AUTO_INCREMENT sequence start with another value, use the following SQL statement:

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To insert a new record into the 'Persons' table, we will NOT have to specify a value for the 'Personid' column (a unique value will be added automatically):

INSERT INTO Persons (FirstName,LastName)
VALUES ('Lars','Monsen');

The SQL statement above would insert a new record into the 'Persons' table. The 'Personid' column would be assigned a unique value. The 'FirstName' column would be set to 'Lars' and the 'LastName' column would be set to 'Monsen'.

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Syntax for SQL Server

The following SQL statement defines the 'Personid' column to be an auto-increment primary key field in the 'Persons' table:

CREATE TABLE Persons (
Personid int IDENTITY(1,1) PRIMARY KEY,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Age int
);

Sql Primary Keys

The MS SQL Server uses the IDENTITY keyword to perform an auto-increment feature.

In the example above, the starting value for IDENTITY is 1, and it will increment by 1 for each new record.

Tip: To specify that the 'Personid' column should start at value 10 and increment by 5, change it to IDENTITY(10,5).

To insert a new record into the 'Persons' table, we will NOT have to specify a value for the 'Personid' column (a unique value will be added automatically):

INSERT INTO Persons (FirstName,LastName)
VALUES ('Lars','Monsen');

Secondary Keys

Syntax for Access

The following SQL statement defines the 'Personid' column to be an auto-increment primary key field in the 'Persons' table:

CREATE TABLE Persons (
Personid AUTOINCREMENT PRIMARY KEY,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Age int
);

The MS Access uses the AUTOINCREMENT keyword to perform an auto-increment feature.

By default, the starting value for AUTOINCREMENT is 1, and it will increment by 1 for each new record.

Tip: To specify that the 'Personid' column should start at value 10 and increment by 5, change the autoincrement to AUTOINCREMENT(10,5).

To insert a new record into the 'Persons' table, we will NOT have to specify a value for the 'Personid' column (a unique value will be added automatically):

INSERT INTO Persons (FirstName,LastName)
VALUES ('Lars','Monsen');

Syntax for Oracle

In Oracle the code is a little bit more tricky.

You will have to create an auto-increment field with the sequence object (this object generates a number sequence).

Use the following CREATE SEQUENCE syntax:

CREATE SEQUENCE seq_person
MINVALUE 1
START WITH 1
INCREMENT BY 1
CACHE 10;

The code above creates a sequence object called seq_person, that starts with 1 and will increment by 1. It will also cache up to 10 values for performance. The cache option specifies how many sequence values will be stored in memory for faster access.

To insert a new record into the 'Persons' table, we will have to use the nextval function (this function retrieves the next value from seq_person sequence):

INSERT INTO Persons (Personid,FirstName,LastName)
VALUES (seq_person.nextval,'Lars','Monsen');