Q
Problem solve Get help with specific problems with your technologies, process and projects.

# A list of IDs in a column

I need to create a table which has a field that contains a list of id's to rows in another table. For example, the table portfolioAcc has a field which holds a list of holding accounts for a customer. I would really appreciate any help - thanks in advance.

This type of structure, in which one table is related to another through multiple IDs or keys that are stored within a single column, usually in a comma-separated list, can easily get you into trouble. For example,

```Customer

id  name     accounts
71  J.Smith   12
72  B.White   14,24
73  K.Baker   16,20,26
75  A.Brown   22

Account
id  type     amount
12  bonds   1047.00
14  stock    937.21
16  bonds   3700.00
20  cash      42.98
22  stock  10456.34
24  cash     211.03
26  stock   2044.65```

So B.White has two accounts, a stock account for 937.21, and a cash account for 211.03.

It is easy enough to see how someone can come up with this design. After all, it's called a one-to-many relationship, and sure enough, each customer has one or more accounts. So at first blush, it does indeed look like a one-to-many relationship.

But, alas, the foreign keys are in the wrong table.

The way to relate tables in a one-to-many relationship is to remember that:

• the "one" table (a.k.a. parent) contains the primary key

• the "many" table (a.k.a. child) contains the foreign key

So the preferred design is:

```Customer

id  name
71  J.Smith
72  B.White
73  K.Baker
75  A.Brown

Account
id  custid  type     amount
12    71    bonds   1047.00
14    72    stock    937.21
16    73    bonds   3700.00
20    73    cash      42.98
22    75    stock  10456.34
24    72    cash     211.03
26    73    stock   2044.65```

Space does not permit a full explanation of all the reasons why the comma-separated list of IDs is a poor design. The main problem is that it makes table joins difficult, if not impossible.

#### Have a question for an expert?

Get answers from a TechTarget expert on whatever's puzzling you.

You will be able to add details on the next page.

#### Start the conversation

Send me notifications when other members comment.

## SearchDataManagement

• ### Dremio Data Lake Engine 4.0 accelerates query performance

Dremio issues a new platform update, defining itself as data lake engine technology that looks to help users connect and query ...

• ### Weighing the use of third-party database administration tools

Database expert Chris Foot details the key reasons why DBAs should consider using third-party database administration to fill ...

• ### InfluxDB Cloud 2.0 expands open source time series database

While the core open source InfluxDB 2.0 project is still in alpha, InfluxData has advanced its cloud service to support new ...

• ### Qlik exec discusses AI and its role in the future of BI

The next major trend in business intelligence will be the increasing impact of augmented intelligence and machine learning, ...

• ### SAP BI platform stays strong due to cloud-based architecture

A cloud-native BI platform along with domain-specific applications that can be embedded to serve the needs of various industries ...

• ### Tableau 2019.3 highlighted by enhanced AI, new data catalog

Tableau released its third-quarter update Wednesday, featuring Explain Data, an enhanced augmented intelligence tool, and Tableau...

## SearchSAP

• ### Navy sails SAP ERP systems to AWS GovCloud

The Navy consolidated 26 various ERP systems onto SAP HANA on the AWS GovCloud, leading to data reduction, lower TCO, and setting...

• ### SAP HANA application collects concussion data for real-time analysis

Protecht, an SAP HANA based system, enables teams in contact sports to measure and analyze data about hits though an IoT sensor ...

• ### S/4HANA public cloud vs. private cloud: Compare the pros, cons

In addition to SAP's on-premises and hybrid models, the vendor offers S/4HANA in public and private clouds. Here's a look at the ...

## SearchSQLServer

• ### SQL Server database design best practices and tips for DBAs

Good database design is a must to meet processing needs in SQL Server systems. In a webinar, consultant Koen Verbeeck offered ...

• ### SQL Server in Azure database choices and what they offer users

SQL Server databases can be moved to the Azure cloud in several different ways. Here's what you'll get from each of the options ...

• ### Using a LEFT OUTER JOIN vs. RIGHT OUTER JOIN in SQL

In this book excerpt, you'll learn LEFT OUTER JOIN vs. RIGHT OUTER JOIN techniques and find various examples for creating SQL ...

## TheServerSide.com

• ### Microsoft vs. IBM: A major shift in Java support

Once an afterthought in the Java community, Microsoft has seemingly overtaken IBM as the preeminent advocate among developers at ...

• ### Guide to practicing cloud-native development

In this guide, learn about cloud-native development -- what it is, how vendors try to exploit it and how to bring it to life with...

• ### Eclipse launches Che 7 IDE for Kubernetes development

The Eclipse Foundation has introduced Eclipse Che 7, a new version of the Eclipse Che cloud-based integrated development ...

## SearchDataCenter

• ### New Dell EPYC servers embrace AMD Rome chips

Dell EMC goes from Naples to Rome with a new line of EPYC servers, including Ready Solutions for high-performance computing and ...

• ### Can next-gen SIEM help cybersecurity initiatives?

More organizations are using SIEM, AI and cloud technology to minimize security breaches. Though despite interest, this ...

• ### IBM z15 mainframe secures data across multi-cloud environments

IBM unveiled the latest in its line of mainframes capable of processing 1 trillion web transactions a day. The IBM z15 ...

## SearchContentManagement

• ### Nintex launches no-code workflow automation tool

Nintex has launched a no-code workflow automation tool, Workflow Generator, in an effort to bridge the gap between IT departments...

• ### Cohesion is latest Acquia acquisition

While Acquia would not provide specifics of the deal, the decision behind the acquisition of Cohesion was the chance to bring ...

• ### 3 things to learn before considering blockchain integration

Paul Swider, CTO at RealActivity LLC, discusses how to use blockchain technology to increase the security and usefulness of ...

## SearchHRSoftware

• ### SuccessFactors customers to see big Qualtrics impact

SuccessFactors is rethinking its HCM suite as it works to integrate Qualtrics into its applications. But HR managers are ...

• ### HiQ Labs vs LinkedIn case OKs robot monitoring of employees

A U.S. Court of Appeals ruled on the LinkedIn vs HiQ lawsuit, which could help shape how services gather information on social ...

• ### MyPayrollHR collapse stirs allegations, questions, anger

The problems created by the closing of MyPayrollHR may take a long time to resolve. The FBI has been contacted and lawsuits are ...

Close