# Using Boolean Operators and Parentheses in Advanced Search

In **Advanced Search**, you can combine searches across multiple fields using **Boolean operators** (AND, OR, NOT) to create long and complex search expressions. This allows you to take full advantage of CABI’s database field structure.

**How the search engine applies Boolean nesting logic**

* **Without parentheses**: The search engine applies Boolean operators **in order of appearance**. It starts with the first field, then applies the next operator and field sequentially down the search string. No assumptions are made about operator precedence.
* **With parentheses**: You can control the order in which Boolean operators are applied by grouping fields or terms with parentheses `(` `)`. This ensures that certain parts of the search are evaluated together before combining them with other fields.

The platform also **recognises parentheses split across multiple fields**.

####

**Simple example: combining fields with OR and AND**

Suppose you want to find articles that:

* Mention Diabetes in the Title OR Insulin in the Abstract,
* AND mention Children in the Indexing Term field.

To ensure correct Boolean nesting:

1. Place an **opening parenthesis `(`** before the first search term (“Diabetes”).
2. Place a **closing parenthesis `)`** after the last term in the second field (“Insulin”).

<figure><img src="/files/8bZ4sWXgohZ8UTH4760A" alt=""><figcaption></figcaption></figure>

This is the search typed as a string showing the Boolean nesting:

(Title: Diabetes OR AB: Insulin) AND IndexingTerm: Children

This is how the search engine interprets it:

Title:((Diabetes) OR AB:(Insulin)) AND IndexingTerm:(Children)

This ensures that the search combines the first two fields with OR before applying the third field with AND, returning results about diabetes or insulin limited to children.

{% hint style="info" %}

<p align="center"><strong>Note</strong>: The search engine automatically groups all terms entered in a single field with parentheses.</p>
{% endhint %}

**Nesting multiple fields**

You can combine several fields using parentheses for more complex searches. For example:

<figure><img src="/files/qU9tCFbOaGF7FADbAJd0" alt=""><figcaption></figcaption></figure>

Title:((Diabetes) OR AllField:(glucose management) OR AB:(Insulin)) AND IndexingTerm:(Children)

Here, three fields are grouped together using parentheses with OR, then combined with the Indexing Term field using AND.

#### **Complex example**

Advanced Search allows very detailed queries across multiple fields. For example, to search for studies about antimicrobial resistance in indigenous peoples in South America, you could use a search that combines multiple terms across four fields with different sets of parentheses, ensuring that all intended relationships between terms are applied correctly:

<figure><img src="/files/CyGSXwABh2TkGAFmOw8r" alt=""><figcaption></figcaption></figure>

Title:(("antimicrobial resistance" OR "antibiotic resistance" OR "drug resistance") OR AB:("antimicrobial resistance" OR "antibiotic resistance" OR "drug resistance")) AND AllField:(("indigenous peoples" OR tribes OR "ethnic groups") AND IndexingTerm:("South America" OR "Latin America"))

In sum, by understanding how parentheses and Boolean operators work, you can construct precise, complex searches in the Advanced Search function to retrieve exactly the records you need.


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