在SQL Server的SQL优化过程中,如果遇到WHERE条件中包含LIKE '%search_string%'是一件非常头痛的事情。这种情况下,一般要修改业务逻辑或改写SQL才能解决SQL执行计划走索引扫描或全表扫描的问题。最近在优化SQL语句的时候,遇到了一个很有意思的问题。某些使用LIKE '%' + @search_string + '%'(或者 LIKE @search_s...
LIKE 操作符不是针对已知值进行过滤的 通配符(wildcard) :用来匹配值的一部分的特殊字符。 搜索模式(search pattern) :由字面值、通配符或两者组合构成的搜索条件。 通配符: 百分号(%):任何字符出现任意次数 下划线(_):它只匹配单个字符,而不是多个字符 方括号([]):指定一个字符集,它必须匹配指定位置(通配符的...
return writer; } private void Search_Click(object sender, EventArgs e) { string key = this.textBox1.Text; IndexSearcher search = new IndexSearcher(@"c:/index/"); //把刚才建立的索引取出来 Term t = new Term("ProductDesc", "*" + key + "*"); WildcardQuery query = new WildcardQuer...
在SQL Server的SQL优化过程中,如果遇到WHERE条件中包含LIKE '%search_string%'是一件非常头痛的事情。这种情况下,一般要修改业务逻辑或改写SQL才能解决SQL执行计划走索引扫描或全表扫描的问题。最近在优化SQL语句的时候,遇到了一个很有意思的问题。某些使用LIKE '%' + @search_string + '%'(或者 LIKE @search_s...
String Overview = (String comparison or assignment) + (String concatenation) += (String concatenation assignment) % (Wildcard - character(s) to match) [ ] (Wildcard - character(s) to match) [^] (Wildcard - character(s) not to match) ...
SQL*Loader-00534: Warning: no files found for INFILE wildcard specification (string).\n Cause: SQL*Loader could not find a file which matched the INFILE wildcard specification. Action: Check to make sure that the files exist in order for them to be loaded. SQL*Loader-00535: Warning:...
string_expression A string of characters and wildcard characters. [ NOT ] LIKE Indicates that the subsequent character string is to be used with pattern matching. For more information, see LIKE. ESCAPE 'escape_ character' Allows for a wildcard character to be searched for in a character string...
These wildcard characters can be used in string comparisons that involve pattern matching, such as LIKE and PATINDEX. Examples A: Simple example The following example uses the [^] operator to find the top 5 people in the Contact table who have a first name that starts with Al and has a...
Returns the string that is used to escape wildcard characters. C# Копирај public string? SearchStringEscape { [Android.Runtime.Register("getSearchStringEscape", "()Ljava/lang/String;", "GetGetSearchStringEscapeHandler:Java.Sql.IDatabaseMetaDataInvoker, Mono.Android, Version=0.0.0.0,...
Examples See Also Matches any string of zero or more characters. This wildcard character can be used as either a prefix or a suffix. For more information, seePattern Matching in Search Conditions. Examples The following example returns all the first names of people in the Contact table of Adv...