head.rst

head

Table of contents

• Description
• Syntax
• Example 1: Get first 10 results
• Example 2: Get first N results
• Example 3: Get first N results with while condition
• Example 4: Get first N results with while condition and last result which failed condition

Description

The head command returns the first N number of specified results in search order.

Syntax

head [keeplast = (true | false)] [while "("<boolean-expression>")"] [N]

• keeplast: optional. use in conjunction with the while argument to determine whether the last result in the result set is retained. The last result returned is the result that caused the <boolean-expression> to evaluate to false or NULL. Set keeplast=true to retain the last result in the result set. Set keeplast=false to discard the last result. Default: true
• while: optional. expression that evaluates to either true or false. statistical functions can not be used in the expression. Default: false
• N: optional. number of results to return. Default: 10

Example 1: Get first 10 results

The example show first 10 results from accounts index.

PPL query:

od> source=accounts | fields firstname, age | head;
fetched rows / total rows = 10/10
+---------------+-----------+
| firstname     | age       |
|---------------+-----------|
| Amber         | 32        |
| Hattie        | 36        |
| Nanette       | 28        |
| Dale          | 33        |
| Elinor        | 36        |
| Virginia      | 39        |
| Dillard       | 34        |
| Mcgee         | 39        |
| Aurelia       | 37        |
| Fulton        | 23        |
+---------------+-----------+

Example 2: Get first N results

The example show first N results from accounts index.

PPL query:

od> source=accounts | fields firstname, age | head 3;
fetched rows / total rows = 3/3
+---------------+-----------+
| firstname     | age       |
|---------------+-----------|
| Amber         | 32        |
| Hattie        | 36        |
| Nanette       | 28        |
+---------------+-----------+

Example 3: Get first N results with while condition

The example show first N results from accounts index with while condition.

PPL query:

od> source=accounts | fields firstname, age | sort age | head while(age < 21) 7;
fetched rows / total rows = 4/4
+---------------+-----------+
| firstname     | age       |
|---------------+-----------|
| Claudia       | 20        |
| Copeland      | 20        |
| Cornelia      | 20        |
| Schultz       | 20        |
| Simpson       | 21        |
+---------------+-----------+

Example 4: Get first N results with while condition and last result which failed condition

The example show first N results with while condition and last result which failed condition.

PPL query:

od> source=accounts | fields firstname, age | sort age | head keeplast=false while(age < 21) 7;
fetched rows / total rows = 4/4
+---------------+-----------+
| firstname     | age       |
|---------------+-----------|
| Claudia       | 20        |
| Copeland      | 20        |
| Cornelia      | 20        |
| Schultz       | 20        |
+---------------+-----------+