Wildcards are used with theLIKEoperator in SQL. The application of wildcard in SQL will be shown in theSQL LIKEsection. Examples Below are some wildcard examples: 'A_Z': All string that starts with 'A', another character, and end with 'Z'. For example, 'ABZ' and 'A2Z' would both...
其实复杂的情况下,LIKE 'search_string%'也有走索引扫描(Index Scan)的情况,上面情况并不是唯一、绝对的。如下所示 在表Person.Person的 rowguid字段上创建有唯一索引AK_Person_rowguid 那么我们来看看上面所说的这个特殊案例(这里使用一个现成的案例,懒得构造案例了),如何让LIKE %search_string%走索引查找(Index Se...
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...
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) ...
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...
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_...
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:...
Matches any single character within the specified range or set that is specified between the brackets. These wildcard characters can be used in string comparisons that involve pattern matching, such as LIKE and PATINDEX. For more information, see Pattern Matching in Search Conditions....
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 AdventureWorks...
Use a wildcard only at the end of a string search value (use STARTS WITH for a LIKE query). Create Oracle Function-based or DB2® Generated Column Indexes for Case-Insensitive string comparisons Join only one or two tables at a time in a query Avoid unnecessary ORDER BY clauses Us...