78 lines
2.4 KiB
Markdown
78 lines
2.4 KiB
Markdown
---
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{
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"title": "substring",
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"language": "en"
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}
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---
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<!--
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Licensed to the Apache Software Foundation (ASF) under one
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or more contributor license agreements. See the NOTICE file
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distributed with this work for additional information
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regarding copyright ownership. The ASF licenses this file
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to you under the Apache License, Version 2.0 (the
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"License"); you may not use this file except in compliance
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with the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing,
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software distributed under the License is distributed on an
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"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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KIND, either express or implied. See the License for the
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specific language governing permissions and limitations
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under the License.
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-->
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## substring
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### description
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#### Syntax
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`VARCHAR substring(VARCHAR str, INT pos[, INT len])`
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The forms without a `len` argument return a substring from string `str` starting at position `pos`.
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The forms with a `len` argument return a substring len characters long from string `str`, starting at position pos.
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It is also possible to use a negative value for `pos`. In this case,
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the beginning of the substring is `pos` characters from the end of the string, rather than the beginning.
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A negative value may be used for `pos` in any of the forms of this function.
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A value of 0 for `pos` returns an empty string.
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For all forms of SUBSTRING(),
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the position of the first character in the string from which the substring is to be extracted is reckoned as 1.
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If len is less than 1, the result is the empty string.
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### example
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```
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mysql> select substring('abc1', -2);
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+-----------------------------+
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| substring('abc1', 2) |
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+-----------------------------+
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| bc1 |
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+-----------------------------+
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mysql> select substring('abc1', -2);
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+-----------------------------+
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| substring('abc1', -2) |
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+-----------------------------+
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| c1 |
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+-----------------------------+
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mysql> select substring('abc1', 5);
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+-----------------------------+
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| substring('abc1', 5) |
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+-----------------------------+
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| NULL |
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+-----------------------------+
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mysql> select substring('abc1def', 2, 2);
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+-----------------------------+
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| substring('abc1def', 2, 2) |
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+-----------------------------+
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| bc |
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+-----------------------------+
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```
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### keywords
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SUBSTRING
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