📅 最后修改于: 2021-01-11 11:20:43 🧑 作者: Mango
Teradata提供了几种操作字符串的功能。这些功能与ANSI标准兼容。
大多数标准字符串函数以及对这些函数的Teradata扩展也都支持Teradata字符串函数。
| String function | Explanation |
|---|---|
| Concat (string1, …, stringN) | It returns the concatenation of two or more string values. This function provides the same functionality as the SQL-standard concatenation operator (||). |
| Length (string) | It returns the number of characters in the string. |
| Lower (string) | It converts a string to lower case. |
| Upper (string) | It converts a string to upper case. |
| Lpad (string, size, padstring) | Pads the left side of the string with characters to create a new string. |
| Rpad (string, size, padstring) | Pads the right side of the string with characters to create a new string. |
| Trim (string) | It removes leading and trailing whitespace from the given string. |
| Ltrim (string) | It removes leading whitespaces from the string. |
| Rtrim (string) | It removes trailing whitespaces from the string. |
| Replace (string, search) | It removes the search string from the given string. |
| Replace (string, search, replace) | It replaces all instances of search with replacing string. |
| Reverse (string) | It returns string characters in reverse order. |
| Split (string, delimiter) | Split given string on the delimiter. This function returns an array of string. |
| Strops (string, substring) | It returns the staring position first instance of a substring in a given string. |
| Position (substring IN string) | It returns the staring position first instance of a substring in a given string. |
| Substr (string, start, length) | It returns a substring of string that begins at the start position and is length characters long. |
| Chr (n) | It returns the character with the specified ASCII value. |
| to_utf8 (string) | It encodes a string into a UTF-8 varbinary representation. |
| from_utf8 (binary) | It decodes a UTF-8 encoded string from binary. |
| Select translate (string, from, to); | It can replace any character in the string that matches a character in the form set with the corresponding character in the set. |
| Index (string) | It locates the position of a character in a string (Teradata extension). |
UPPER和LOWER函数分别将字符列值全部转换为大写和小写。 UPPER和LOWER符合ANSI。
句法
UPPER (expression) -> returns expression as uppercase
LOWER (expression) -> returns expression as lowercase
例
下面的例子将“罗伯特”字符串转换的大写字符串。
/*create a table called NAMES */
CREATE TABLE NAMES(Name text);
/*create few records in this table */
SELECT UPPER('Robert');
/*Query completed. One row found. One column returned */
/*Total elapsed time was 0.00 second */
/*Display all the records from the table */
SELECT * FROM NAMES;
执行完上面的代码后，它将给出以下输出。
ROBERT
现在，在同一示例中，我们将在小写字符串字符串中转换相同的“ ROBERT”字符串。
SELECT LOWER('ROBERT');
/*Query completed. One row found. One column returned */
/*Total elapsed time was 0.00 second */
输出量
robert
所述CHARACTER_LENGTH函数返回<字符>表达式的字符的数目。
句法
CHARACTER_LENGTH (expression)
例
下面的例子将返回“罗伯特”字符串的字符数。
SELECT CHARACTER_LENGTH('Robert');
/* Query completed. One row found. One column returned */
/* Total elapsed time was 0.00 second */
执行上面的代码，它告诉“ Robert”字符串的长度，如下所示。
6
TRIM函数用于从表达式中删除特定的前导或尾随或两者之间的空间。 TRIM是ANSI标准。
句法
TRIM ([LEADING | BOTH | TRAILING] [trim_character ] FROM expression)
例
以下示例从“ Robert”字符串的两端删除空格。
SELECT TRIM(' Robert ');
/* Query completed. One row found. One column returned */
/* Total elapsed time was 0.00 second */
当我们执行上面的代码时，它将从字符串的两端修剪掉现有的空间并给出以下输出。
Robert
POSITION函数用于返回子字符串在字符串的位置。仅返回第一次出现的字符串的位置。
句法
POSITION (substr IN str)
例
下面的示例将在“ Robert”字符串返回出现的“ e”。
SELECT POSITION("e" IN "Robert");
/* Query completed. One row found. One column returned */
/* Total elapsed time was 0.00 second */
执行完上面的代码后，它将在“ Robert”字符串找到“ e”子字符串的位置作为输出。
4
SUBSTRING函数用于从给定字符串的特定位置返回指定数量的字符。 SUBSTRING函数是ANSI标准。
句法
SUBSTRING (str FROM pos FOR len)
它返回一个字符串(str)，从位置(pos)开始，以字符长度(len)。
例
以下示例返回从3个字符第1个位置处的字符。
SELECT SUBSTRING('Robert' FROM 1 FOR 3);
/* Query completed. One row found. One column returned */
/* Total elapsed time was 0.00 second */
上面的代码从字符串“ Robert”的第一个位置返回3个字符作为输出。
Rob