mirror of https://github.com/apache/druid.git
[Docs] Batch08: adding examples to string functions (#16871)
* batch08 completed * reviewing batch08 * apply corrections suggestions by @FrankChen021
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Edgar Melendrez
GitHub
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@ -597,11 +597,30 @@ Returns true if the expression is contained in a Base64-serialized Bloom filter.
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## BTRIM
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`BTRIM(<CHARACTER>, [<CHARACTER>])`
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Trims characters from both the leading and trailing ends of an expression. Defaults `chars` to a space if none is provided.
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**Function type:** [Scalar, string](sql-scalar.md#string-functions)
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* **Syntax:** `BTRIM(expr[, chars])`
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* **Function type:** Scalar, string
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Trims characters from both the leading and trailing ends of an expression.
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<details><summary>Example</summary>
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The following example trims the `_` characters from both ends of the string expression.
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```sql
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SELECT
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'___abc___' AS "original_string",
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BTRIM('___abc___', '_') AS "trim_both_ends"
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```
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Returns the following:
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| `original_string` | `trim_both_ends` |
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| -- | -- |
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| `___abc___` | `abc` |
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</details>
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[Learn more](sql-scalar.md#string-functions)
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## CASE
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@ -1549,11 +1568,30 @@ Returns the leftmost number of characters from an expression, optionally padded
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## LTRIM
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`LTRIM(<CHARACTER>, [<CHARACTER>])`
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Trims characters from the leading end of an expression. Defaults `chars` to a space if none is provided.
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**Function type:** [Scalar, string](sql-scalar.md#string-functions)
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* **Syntax:** `LTRIM(expr[, chars])`
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* **Function type:** Scalar, string
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Trims characters from the leading end of an expression.
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<details><summary>Example</summary>
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The following example trims the `_` characters from the leading end of the string expression.
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```sql
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SELECT
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'___abc___' AS "original_string",
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LTRIM('___abc___', '_') AS "trim_leading_end_of_expression"
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```
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Returns the following:
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| `original_string` | `trim_leading_end_of_expression` |
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| -- | -- |
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| `___abc___` | `abc___` |
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</details>
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[Learn more](sql-scalar.md#string-functions)
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## MAX
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@ -1859,28 +1897,85 @@ string may refer to capture groups using `$1`, `$2`, etc.
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## REPEAT
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`REPEAT(<CHARACTER>, [<INTEGER>])`
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Repeats the string expression `N` times, where `N` is an integer.
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**Function type:** [Scalar, string](sql-scalar.md#string-functions)
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* **Syntax:** `REPEAT(expr, N)`
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* **Function type:** Scalar, string
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Repeats the string expression an integer number of times.
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<details><summary>Example</summary>
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The following example returns the string expression `abc` repeated `3` times.
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```sql
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SELECT
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'abc' AS "original_string",
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REPEAT('abc', 3) AS "with_repetition"
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```
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Returns the following:
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| `original_string` | `with_repetition` |
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| -- | -- |
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| `abc` | `abcabcabc` |
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</details>
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[Learn more](sql-scalar.md#string-functions)
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## REPLACE
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`REPLACE(expr, pattern, replacement)`
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Replaces instances of a substring with a replacement string in the given expression.
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**Function type:** [Scalar, string](sql-scalar.md#string-functions)
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* **Syntax:** `REPLACE(expr, substring, replacement)`
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* **Function type:** Scalar, string
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Replaces a pattern with another string in the given expression.
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<details><summary>Example</summary>
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The following example replaces instances of the substring `abc` with `XYZ`.
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```sql
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SELECT
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'abc 123 abc 123' AS "original_string",
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REPLACE('abc 123 abc 123', 'abc', 'XYZ') AS "modified_string"
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```
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Returns the following:
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| `original_string` | `modified_string` |
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| -- | -- |
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| `abc 123 abc 123` | `XYZ 123 XYZ 123` |
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</details>
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[Learn more](sql-scalar.md#string-functions)
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## REVERSE
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`REVERSE(expr)`
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**Function type:** [Scalar, string](sql-scalar.md#string-functions)
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Reverses the given expression.
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* **Syntax:** `REVERSE(expr)`
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* **Function type:** Scalar, string
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<details><summary>Example</summary>
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The following example reverses the string expression `abc`.
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```sql
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SELECT
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'abc' AS "original_string",
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REVERSE('abc') AS "reversal"
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```
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Returns the following:
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| `original_string` | `reversal` |
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| -- | -- |
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| `abc` | `cba` |
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</details>
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[Learn more](sql-scalar.md#string-functions)
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## RIGHT
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Returns the `N` rightmost characters of an expression, where `N` is an integer value.
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@ -1954,11 +2049,30 @@ Returns the rightmost number of characters from an expression, optionally padded
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## RTRIM
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`RTRIM(<CHARACTER>, [<CHARACTER>])`
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Trims characters from the trailing end of an expression. Defaults `chars` to a space if none is provided.
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**Function type:** [Scalar, string](sql-scalar.md#string-functions)
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* **Syntax:** `RTRIM(expr[, chars])`
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* **Function type:** Scalar, string
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Trims characters from the trailing end of an expression.
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<details><summary>Example</summary>
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The following example trims the `_` characters from the trailing end of the string expression.
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```sql
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SELECT
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'___abc___' AS "original_string",
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RTRIM('___abc___', '_') AS "trim_end"
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```
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Returns the following:
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| `original_string` | `trim_end` |
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| -- | -- |
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| `___abc___` | `___abc` |
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</details>
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[Learn more](sql-scalar.md#string-functions)
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## SAFE_DIVIDE
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@ -2074,11 +2188,33 @@ Splits `str1` into an array on the delimiter specified by `str2`, which is a reg
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## STRING_FORMAT
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`STRING_FORMAT(pattern[, args...])`
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Returns a string formatted in the manner of Java's [String.format](https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#format-java.lang.String-java.lang.Object...-).
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**Function type:** [Scalar, string](sql-scalar.md#string-functions)
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* **Syntax:** `STRING_FORMAT(pattern[, args...])`
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* **Function type:** Scalar, string
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Returns a string formatted in accordance to Java's String.format method.
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<details><summary>Example</summary>
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The following example uses Java String format to pass in `Flight_Number_Reporting_Airline` and `origin_airport` columns, from the `flight-carriers` datasource, as arguments into the string.
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```sql
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SELECT
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"Flight_Number_Reporting_Airline" AS "flight_number",
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"Origin" AS "origin_airport",
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STRING_FORMAT('Flight No.%d departing from %s', "Flight_Number_Reporting_Airline", "Origin") AS "departure_announcement"
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FROM "flight-carriers"
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LIMIT 1
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```
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Returns the following:
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| `flight_number` | `origin_airport` | `departure_announcement` |
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| -- | -- | -- |
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| `314` | `SJU` | `Flight No.314 departing from SJU` |
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</details>
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[Learn more](sql-scalar.md#string-functions)
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## STRING_TO_MV
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@ -2099,27 +2235,69 @@ Alias for [`LENGTH`](#length).
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## STRPOS
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`STRPOS(<CHARACTER>, <CHARACTER>)`
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Returns the one-based index position of a substring within an expression. If `substring` is not found, returns 0.
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**Function type:** [Scalar, string](sql-scalar.md#string-functions)
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* **Syntax:** `STRPOS(expr, substring)`
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* **Function type:** Scalar, string
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Returns the one-based index position of a substring within an expression.
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<details><summary>Example</summary>
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The following example returns the one-based index position of `World`.
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```sql
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SELECT
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'Hello World!' AS "original_string",
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STRPOS('Hello World!', 'World') AS "index"
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```
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Returns the following:
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| `original_string` | `index` |
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| -- | -- |
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| `Hello World!` | `7` |
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</details>
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[Learn more](sql-scalar.md#string-functions)
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## SUBSTR
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`SUBSTR(<CHARACTER>, <INTEGER>, [<INTEGER>])`
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**Function type:** [Scalar, string](sql-scalar.md#string-functions)
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Alias for [`SUBSTRING`](#substring).
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* **Syntax:** `SUBSTR(expr, index[, length])`
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* **Function type:** Scalar, string
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[Learn more](sql-scalar.md#string-functions)
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## SUBSTRING
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`SUBSTRING(<CHARACTER>, <INTEGER>, [<INTEGER>])`
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Returns a substring of the expression starting at a given one-based index. If `length` is omitted, extracts characters to the end of the string, otherwise returns a substring of `length` characters.
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**Function type:** [Scalar, string](sql-scalar.md#string-functions)
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* **Syntax:** `SUBSTRING(expr, index[, length])`
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* **Function type:** Scalar, string
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Returns a substring of the expression starting at a given one-based index.
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<details><summary>Example</summary>
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The following example extracts a substring from the string expression `abcdefghi` of length `3` starting at index `4`
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```sql
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SELECT
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'abcdefghi' AS "original_string",
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SUBSTRING('abcdefghi', 4, 3) AS "substring"
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```
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Returns the following:
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| `original_string` | `substring` |
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| -- | -- |
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| `abcdefghi` | `def` |
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</details>
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[Learn more](sql-scalar.md#string-functions)
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## SUM
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**Function type:** [JSON](sql-json-functions.md)
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`TO_JSON_STRING(expr)`
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Serializes `expr` into a JSON string.
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## TRIM
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`TRIM([BOTH|LEADING|TRAILING] [<chars> FROM] expr)`
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Trims the leading and/or trailing characters of an expression. Defaults `chars` to a space if none is provided. Defaults to `BOTH` if no directional argument is provided.
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**Function type:** [Scalar, string](sql-scalar.md#string-functions)
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* **Syntax:** `TRIM([BOTH|LEADING|TRAILING] [chars FROM] expr)`
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* **Function type:** Scalar, string
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Trims the leading or trailing characters of an expression.
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<details><summary>Example</summary>
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The following example trims `_` characters from both ends of the string expression.
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```sql
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SELECT
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'___abc___' AS "original_string",
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TRIM( BOTH '_' FROM '___abc___') AS "trim_expression"
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```
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Returns the following:
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| `original_string` | `trim_expression` |
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| -- | -- |
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| `___abc___` | `abc` |
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</details>
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[Learn more](sql-scalar.md#string-functions)
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## TRUNC
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@ -112,12 +112,12 @@ String functions accept strings and return a type appropriate to the function.
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|`REGEXP_EXTRACT(expr, pattern[, index])`|Apply regular expression `pattern` to `expr` and extract a capture group or `NULL` if there is no match. If `index` is unspecified or zero, returns the first substring that matched the pattern. The pattern may match anywhere inside `expr`. To match the entire string, use the `^` and `$` markers at the start and end of your pattern. When `druid.generic.useDefaultValueForNull = true`, it is not possible to differentiate an empty-string match from a non-match (both return `NULL`).|
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|`REGEXP_LIKE(expr, pattern)`|Returns whether `expr` matches regular expression `pattern`. The pattern may match anywhere inside `expr`; if you want to match the entire string instead, use the `^` and `$` markers at the start and end of your pattern. Similar to [`LIKE`](sql-operators.md#logical-operators), but uses regexps instead of LIKE patterns. Especially useful in WHERE clauses.|
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|`REGEXP_REPLACE(expr, pattern, replacement)`|Replaces all occurrences of regular expression `pattern` within `expr` with `replacement`. The replacement string may refer to capture groups using `$1`, `$2`, etc. The pattern may match anywhere inside `expr`; if you want to match the entire string instead, use the `^` and `$` markers at the start and end of your pattern.|
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|`REPLACE(expr, pattern, replacement)`|Replaces pattern with replacement in `expr`, and returns the result.|
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|`REPLACE(expr, substring, replacement)`|Replaces instances of `substring` in `expr` with `replacement` and returns the result.|
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|`REPEAT(expr, N)`|Repeats `expr` `N` times.|
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|`REVERSE(expr)`|Reverses `expr`.|
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|`STRING_FORMAT(pattern[, args...])`|Returns a string formatted in the manner of Java's [String.format](https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#format-java.lang.String-java.lang.Object...-).|
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|`STRPOS(haystack, needle)`|Returns the index of `needle` within `haystack`, with indexes starting from 1. If `needle` is not found, returns 0.|
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|`SUBSTRING(expr, index[, length])`|Returns a substring of `expr` starting at `index`, with a max `length`, both measured in UTF-16 code units.|
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|`STRPOS(expr, substring)`|Returns the index of `substring` within `expr`, with indexes starting from 1. If `substring` is not found, returns 0.|
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|`SUBSTRING(expr, index[, length])`|Returns a substring of `expr` starting at a given one-based index. If `length` is omitted, extracts characters to the end of the string, otherwise returns a substring of `length` UTF-16 characters.|
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|`SUBSTR(expr, index[, length])`|Alias for `SUBSTRING`.|
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|`TRIM([BOTH `<code>|</code>` LEADING `<code>|</code>` TRAILING] [chars FROM] expr)`|Returns `expr` with characters removed from the leading, trailing, or both ends of `expr` if they are in `chars`. If `chars` is not provided, it defaults to `''` (a space). If the directional argument is not provided, it defaults to `BOTH`.|
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|`BTRIM(expr[, chars])`|Alternate form of `TRIM(BOTH chars FROM expr)`.|
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