<commit_before>---
title: Frequently Asked Questions
aliases:
  - /influxdb/v1.2/troubleshooting/frequently_encountered_issues/

menu:
  influxdb_1_2:
    weight: 0
    parent: troubleshooting
---

This page addresses frequent sources of confusion and places where InfluxDB behaves in an unexpected way relative to other database systems.
Where applicable, it links to outstanding issues on GitHub.

**Administration**  

* [How do I include a single quote in a password?](#how-do-i-include-a-single-quote-in-a-password)  
* [How can I identify my version of InfluxDB?](#how-can-i-identify-my-version-of-influxdb)  
* [Where can I find InfluxDB logs?](#where-can-i-find-influxdb-logs)
* [What is the relationship between shard group durations and retention policies?](#what-is-the-relationship-between-shard-group-durations-and-retention-policies)
* [Why aren't data dropped after I've altered a retention policy?](#why-aren-t-data-dropped-after-i-ve-altered-a-retention-policy)
* [Why does InfluxDB fail to parse microsecond units in the configuration file?](#why-does-influxdb-fail-to-parse-microsecond-units-in-the-configuration-file)

**Command Line Interface (CLI)**

* [How do I make InfluxDB’s CLI return human readable timestamps?](#how-do-i-make-influxdb-s-cli-return-human-readable-timestamps)  
* [How can a non-admin user `USE` a database in InfluxDB's CLI?](#how-can-a-non-admin-user-use-a-database-in-influxdb-s-cli)  
* [How do I write to a non-`DEFAULT` retention policy with InfluxDB's CLI?](#how-do-i-write-to-a-non-default-retention-policy-with-influxdb-s-cli)

**Data Types**

* [Why can't I query boolean field values?](#why-can-t-i-query-boolean-field-values)  
* [How does InfluxDB handle field type discrepancies across shards?](#how-does-influxdb-handle-field-type-discrepancies-across-shards)  
* [What are the minimum and maximum integers that InfluxDB can store?](#what-are-the-minimum-and-maximum-integers-that-influxdb-can-store)  
* [What are the minimum and maximum timestamps that InfluxDB can store?](#what-are-the-minimum-and-maximum-timestamps-that-influxdb-can-store)
* [How can I tell what type of data are stored in a field?](#how-can-i-tell-what-type-of-data-are-stored-in-a-field)
* [Can I change a field's data type?](#can-i-change-a-field-s-data-type)

**InfluxQL Functions**

* [How do I perform mathematical operations within a function?](#how-do-i-perform-mathematical-operations-within-a-function)  
* [Why does my query return epoch 0 as the timestamp?](#why-does-my-query-return-epoch-0-as-the-timestamp)   
* [Which InfluxQL functions support nesting?](#which-influxql-functions-support-nesting)

**Querying Data**  

* [What determines the time intervals returned by `GROUP BY time()` queries?](#what-determines-the-time-intervals-returned-by-group-by-time-queries)  
* [Why do my queries return no data or partial data?](#why-do-my-queries-return-no-data-or-partial-data)
* [Why don't my `GROUP BY time()` queries return timestamps that occur after `now()`?](#why-don-t-my-group-by-time-queries-return-timestamps-that-occur-after-now)  
* [Can I perform mathematical operations against timestamps?](#can-i-perform-mathematical-operations-against-timestamps)  
* [Can I identify write precision from returned timestamps?](#can-i-identify-write-precision-from-returned-timestamps)  
* [When should I single quote and when should I double quote in queries?](#when-should-i-single-quote-and-when-should-i-double-quote-in-queries)  
* [Why am I missing data after creating a new `DEFAULT` retention policy?](#why-am-i-missing-data-after-creating-a-new-default-retention-policy)
* [Why is my query with a `WHERE OR` time clause returning empty results?](#why-is-my-query-with-a-where-or-time-clause-returning-empty-results)
* [Why does `fill(previous)` return empty results?](#why-does-fill-previous-return-empty-results)
* [Why are my `INTO` queries missing data?](#why-are-my-into-queries-missing-data)
* [How do I query data with an identical tag key and field key?](#how-do-i-query-data-with-an-identical-tag-key-and-field-key)
* [How do I query data across measurements?](#how-do-i-query-data-across-measurements)
* [Does the order of the timestamps matter?](#does-the-order-of-the-timestamps-matter)
* [How do I `SELECT` data with a tag that has no value?](#how-do-i-select-data-with-a-tag-that-has-no-value)

**Series and Series Cardinality**

* [How can I query for series cardinality?](#how-can-i-query-for-series-cardinality)  
* [Why does series cardinality matter?](#why-does-series-cardinality-matter)  
* [How can I remove series from the index?](#how-can-i-remove-series-from-the-index)

**Writing Data**  

* [How do I write integer field values?](#how-do-i-write-integer-field-values)   
* [How does InfluxDB handle duplicate points?](#how-does-influxdb-handle-duplicate-points)  
* [What newline character does the HTTP API require?](#what-newline-character-does-the-http-api-require)
* [What words and characters should I avoid when writing data to InfluxDB?](#what-words-and-characters-should-i-avoid-when-writing-data-to-influxdb)  
* [When should I single quote and when should I double quote when writing data?](#when-should-i-single-quote-and-when-should-i-double-quote-when-writing-data)  
* [Does the precision of the timestamp matter?](#does-the-precision-of-the-timestamp-matter)
* [What are the configuration recommendations and schema guidelines for writing sparse, historical data?](#what-are-the-configuration-recommendations-and-schema-guidelines-for-writing-sparse-historical-data)

## How do I include a single quote in a password?
Escape the single quote with a backslash (`\`) both when creating the password
and when authentication requests.

## How can I identify my version of InfluxDB?
There a number of ways to identify the version of InfluxDB that you're using:

#### Run `influxd version` in your terminal:
```
$ influxd version

InfluxDB ✨ v1.2.0 ✨ (git: master b7bb7e8359642b6e071735b50ae41f5eb343fd42)
```

#### `curl` the `/ping` endpoint:

```
$ url -i 'http://localhost:8086/ping'

HTTP/1.1 204 No Content
Content-Type: application/json
Request-Id: 1e08aeb6-fec0-11e6-8486-000000000000
✨ X-Influxdb-Version: 1.2.0 ✨
Date: Wed, 01 Mar 2017 20:46:17 GMT
```

#### Launch InfluxDB's [Command Line Interface](/influxdb/v1.2/tools/shell/):

```
$ influx

Connected to http://localhost:8086✨ version 1.2.0 ✨  
InfluxDB shell version: 1.2.0
```

#### Check the HTTP response in your logs:  <commit_msg>Address missing "c" in curl command<commit_after>---
title: Frequently Asked Questions
aliases:
  - /influxdb/v1.2/troubleshooting/frequently_encountered_issues/

menu:
  influxdb_1_2:
    weight: 0
    parent: troubleshooting
---

This page addresses frequent sources of confusion and places where InfluxDB behaves in an unexpected way relative to other database systems.
Where applicable, it links to outstanding issues on GitHub.

**Administration**  

* [How do I include a single quote in a password?](#how-do-i-include-a-single-quote-in-a-password)  
* [How can I identify my version of InfluxDB?](#how-can-i-identify-my-version-of-influxdb)  
* [Where can I find InfluxDB logs?](#where-can-i-find-influxdb-logs)
* [What is the relationship between shard group durations and retention policies?](#what-is-the-relationship-between-shard-group-durations-and-retention-policies)
* [Why aren't data dropped after I've altered a retention policy?](#why-aren-t-data-dropped-after-i-ve-altered-a-retention-policy)
* [Why does InfluxDB fail to parse microsecond units in the configuration file?](#why-does-influxdb-fail-to-parse-microsecond-units-in-the-configuration-file)

**Command Line Interface (CLI)**

* [How do I make InfluxDB’s CLI return human readable timestamps?](#how-do-i-make-influxdb-s-cli-return-human-readable-timestamps)  
* [How can a non-admin user `USE` a database in InfluxDB's CLI?](#how-can-a-non-admin-user-use-a-database-in-influxdb-s-cli)  
* [How do I write to a non-`DEFAULT` retention policy with InfluxDB's CLI?](#how-do-i-write-to-a-non-default-retention-policy-with-influxdb-s-cli)

**Data Types**

* [Why can't I query boolean field values?](#why-can-t-i-query-boolean-field-values)  
* [How does InfluxDB handle field type discrepancies across shards?](#how-does-influxdb-handle-field-type-discrepancies-across-shards)  
* [What are the minimum and maximum integers that InfluxDB can store?](#what-are-the-minimum-and-maximum-integers-that-influxdb-can-store)  
* [What are the minimum and maximum timestamps that InfluxDB can store?](#what-are-the-minimum-and-maximum-timestamps-that-influxdb-can-store)
* [How can I tell what type of data are stored in a field?](#how-can-i-tell-what-type-of-data-are-stored-in-a-field)
* [Can I change a field's data type?](#can-i-change-a-field-s-data-type)

**InfluxQL Functions**

* [How do I perform mathematical operations within a function?](#how-do-i-perform-mathematical-operations-within-a-function)  
* [Why does my query return epoch 0 as the timestamp?](#why-does-my-query-return-epoch-0-as-the-timestamp)   
* [Which InfluxQL functions support nesting?](#which-influxql-functions-support-nesting)

**Querying Data**  

* [What determines the time intervals returned by `GROUP BY time()` queries?](#what-determines-the-time-intervals-returned-by-group-by-time-queries)  
* [Why do my queries return no data or partial data?](#why-do-my-queries-return-no-data-or-partial-data)
* [Why don't my `GROUP BY time()` queries return timestamps that occur after `now()`?](#why-don-t-my-group-by-time-queries-return-timestamps-that-occur-after-now)  
* [Can I perform mathematical operations against timestamps?](#can-i-perform-mathematical-operations-against-timestamps)  
* [Can I identify write precision from returned timestamps?](#can-i-identify-write-precision-from-returned-timestamps)  
* [When should I single quote and when should I double quote in queries?](#when-should-i-single-quote-and-when-should-i-double-quote-in-queries)  
* [Why am I missing data after creating a new `DEFAULT` retention policy?](#why-am-i-missing-data-after-creating-a-new-default-retention-policy)
* [Why is my query with a `WHERE OR` time clause returning empty results?](#why-is-my-query-with-a-where-or-time-clause-returning-empty-results)
* [Why does `fill(previous)` return empty results?](#why-does-fill-previous-return-empty-results)
* [Why are my `INTO` queries missing data?](#why-are-my-into-queries-missing-data)
* [How do I query data with an identical tag key and field key?](#how-do-i-query-data-with-an-identical-tag-key-and-field-key)
* [How do I query data across measurements?](#how-do-i-query-data-across-measurements)
* [Does the order of the timestamps matter?](#does-the-order-of-the-timestamps-matter)
* [How do I `SELECT` data with a tag that has no value?](#how-do-i-select-data-with-a-tag-that-has-no-value)

**Series and Series Cardinality**

* [How can I query for series cardinality?](#how-can-i-query-for-series-cardinality)  
* [Why does series cardinality matter?](#why-does-series-cardinality-matter)  
* [How can I remove series from the index?](#how-can-i-remove-series-from-the-index)

**Writing Data**  

* [How do I write integer field values?](#how-do-i-write-integer-field-values)   
* [How does InfluxDB handle duplicate points?](#how-does-influxdb-handle-duplicate-points)  
* [What newline character does the HTTP API require?](#what-newline-character-does-the-http-api-require)
* [What words and characters should I avoid when writing data to InfluxDB?](#what-words-and-characters-should-i-avoid-when-writing-data-to-influxdb)  
* [When should I single quote and when should I double quote when writing data?](#when-should-i-single-quote-and-when-should-i-double-quote-when-writing-data)  
* [Does the precision of the timestamp matter?](#does-the-precision-of-the-timestamp-matter)
* [What are the configuration recommendations and schema guidelines for writing sparse, historical data?](#what-are-the-configuration-recommendations-and-schema-guidelines-for-writing-sparse-historical-data)

## How do I include a single quote in a password?
Escape the single quote with a backslash (`\`) both when creating the password
and when authentication requests.

## How can I identify my version of InfluxDB?
There a number of ways to identify the version of InfluxDB that you're using:

#### Run `influxd version` in your terminal:
```
$ influxd version

InfluxDB ✨ v1.2.0 ✨ (git: master b7bb7e8359642b6e071735b50ae41f5eb343fd42)
```

#### `curl` the `/ping` endpoint:

```
$ curl -i 'http://localhost:8086/ping'

HTTP/1.1 204 No Content
Content-Type: application/json
Request-Id: 1e08aeb6-fec0-11e6-8486-000000000000
✨ X-Influxdb-Version: 1.2.0 ✨
Date: Wed, 01 Mar 2017 20:46:17 GMT
```

#### Launch InfluxDB's [Command Line Interface](/influxdb/v1.2/tools/shell/):

```
$ influx

Connected to http://localhost:8086✨ version 1.2.0 ✨  
InfluxDB shell version: 1.2.0
```

#### Check the HTTP response in your logs:  
{'fraction_non_alphanumeric': 0.1348712033833141, 'fraction_numerical': 0.014763552479815456, 'mean_word_length': 4.699386503067485, 'pattern_counts': {'":': 0, '<': 3, '<?xml version=': 0, '>': 3, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 2, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
{'dir': 'git-commits-cleaned', 'id': '258389', 'n_tokens_mistral': 4610, 'n_tokens_neox': 4255, 'n_words': 1145}