sql-like | 易学教程

What is Full Text Search vs LIKE

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问题 I just read a post mentioning "full text search" in SQL. I was just wondering what the difference between FTS and LIKE are. I did read a couple of articles but couldn't find anything that explained it well. 回答1: In general, there is a tradeoff between "precision" and "recall". High precision means that fewer irrelevant results are presented (no false positives), while high recall means that fewer relevant results are missing (no false negatives). Using the LIKE operator gives you 100%

List of special characters for SQL LIKE clause

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What is the complete list of all special characters for a SQL (I'm interested in SQL Server but other's would be good too) LIKE clause? E.g. SELECT Name FROM Person WHERE Name LIKE '%Jon%' SQL Server : % _ [specifier] E.g. [a-z] [^specifier] ESCAPE clause E.g. %30!%%' ESCAPE '!' will evaluate 30% as true ' characters need to be escaped with ' E.g. they're becomes they''re MySQL: % - Any string of zero or more characters. _ - Any single character ESCAPE clause E.g. %30!%%' ESCAPE '!' will evaluate 30% as true Oracle: % - Any string of zero or more characters. _ - Any single character ESCAPE

MySQL join query using like?

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问题 I have been trying to get this working for quite a while now but it just doesn\'t seem to work, maybe it is is not even possible, what i am wanting to do is to perform a MySQL join query using like, such as this example i found... SELECT * FROM Table1 INNER JOIN Table2 ON Table1.col LIKE \'%\' + Table2.col + \'%\' but it just doesn\'t seem to work at all, any help that can be given would be brilliant, thanks ! 回答1: Try SELECT * FROM Table1 INNER JOIN Table2 ON Table1.col LIKE CONCAT('%',

Performance of like '%Query%' vs full text search CONTAINS query

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问题 I have a situation where I would like to search a single word . For that scenario, which query would be good from a performance point of view? Select Col1, Col2 from Table Where Col1 Like \'%Search%\' or Select Col1, Col2 from Table Where Col1 CONTAINS(Col1,\'Search\') ? 回答1: Full Text Searching (using the CONTAINS) will be faster/more efficient than using LIKE with wildcarding. Full Text Searching (FTS) includes the ability to define Full Text Indexes, which FTS can use. Dunno why you wouldn

Combine PHP prepared statments with LIKE

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问题 Anyone know how to combine PHP prepared statements with LIKE? i.e. \"SELECT * FROM table WHERE name LIKE %?%\"; 回答1: The % signs need to go in the variable that you assign to the parameter, instead of in the query. I don't know if you're using mysqli or PDO, but with PDO it would be something like: $st = $db->prepare("SELECT * FROM table WHERE name LIKE ?"); $st->execute(array('%'.$test_string.'%')); EDIT :: For mysqli user the following. $test_string = '%' . $test_string . '%'; $st->bind

Microsoft office Access `LIKE` VS `RegEx`

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问题 I have been having trouble with the Access key term LIKE and it\'s use. I want to use the following RegEx (Regular Expression) in query form as a sort of \"verfication rule\" where the LIKE operator filters my results: \"^[0]{1}[0-9]{8,9}$\" How can this be accomplished? 回答1: I don't think Access allows regex matches (except in VBA, but that's not what you're asking). The LIKE operator doesn't even support alternation. Therefore you need to split it up into two expressions. ... WHERE (Blah

Escape a string in SQL Server so that it is safe to use in LIKE expression

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How do I escape a string in SQL Server's stored procedure so that it is safe to use in LIKE expression. Suppose I have an NVARCHAR variable like so: declare @myString NVARCHAR(100); And I want to use it in a LIKE expression: ... WHERE ... LIKE '%' + @myString + '%'; How do I escape the string (more specifically, characters that are meaningful to LIKE pattern matching, e.g. % or ? ) in T-SQL, so that it is safe to use in this manner? For example, given: @myString = 'aa%bb' I want: WHERE ... LIKE '%' + @somehowEscapedMyString + '%' to match 'aa%bb' , 'caa%bbc' but not 'aaxbb' or 'caaxbb' . To

Emulating SQL LIKE in JavaScript

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问题 How can I emulate the SQL keyword LIKE in JavaScript? For those of you who don\'t know what LIKE is, it\'s a very simple regex which only supports the wildcards % , which matches 0 or more characters, and _ which matches exactly one character. However, it\'s not just possible to do something like: var match = new RegEx(likeExpr.replace(\"%\", \".*\").replace(\"_\", \".\")).exec(str) != null; ...because the pattern might contain dots, stars and any other special regex characters. 回答1: What you

Which is faster — INSTR or LIKE?

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问题 If your goal is to test if a string exists in a MySQL column (of type \'varchar\', \'text\', \'blob\', etc) which of the following is faster / more efficient / better to use, and why? Or, is there some other method that tops either of these? INSTR( columnname, \'mystring\' ) > 0 vs columnname LIKE \'%mystring%\' 回答1: FULLTEXT searches are absolutely going to be faster, as kibibu noted in the comments above. However : mysql> select COUNT(ID) FROM table WHERE INSTR(Name,'search') > 0; +--------

Is the LIKE operator case-sensitive with MSSQL Server?

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问题 In the documentation about the LIKE operator, nothing is told about the case-sensitivity of it. Is it? How to enable/disable it? I am querying varchar(n) columns, on an Microsoft SQL Server 2005 installation, if that matters. 回答1: It is not the operator that is case sensitive, it is the column itself. When a SQL Server installation is performed a default collation is chosen to the instance. Unless explicitly mentioned otherwise (check the collate clause bellow) when a new database is created