delphi开发环境，写SQL的查询语句，这个单引号是怎么用的，如下

SQLString :=
‘SELECT * FROM XXX_XX_XXXX_STATUS_CHANGE_HIST ‘+
‘WHERE RESISTNAME LIKE ‘‘‘+ComboBox1.Text+‘‘‘||‘‘%‘‘ ‘+
‘AND BATCHNO LIKE ‘‘‘+ComboBox4.Text+‘‘‘||‘‘%‘‘ ‘+
‘AND BOTTLENO LIKE ‘‘‘+ComboBox2.Text+‘‘‘||‘‘%‘‘ ‘+
‘AND EQPID LIKE ‘‘‘+ComboBox3.Text+‘‘‘||‘‘%‘‘ ‘+
‘AND STATUS LIKE ‘‘‘+ComboBox5.Text+‘‘‘||‘‘%‘‘ ‘+
‘AND MODIFYTIME > ‘‘‘+(FormatDateTime(‘yyyy-mm-dd‘,DateTimePicker1.date))+‘‘‘ ‘+
‘AND MODIFYTIME <‘‘‘+(FormatDateTime(‘yyyy-mm-dd‘,DateTimePicker2.date+1))+‘‘‘ ‘+
‘ORDER BY MODIFYTIME DESC‘;

两个表示包含了单引号这个符号。
举例：
a:=‘abc‘;
那么a里面实际存的是：abc

b:=‘‘‘abc‘‘‘;
那么b里面实际存的是：‘abc‘

c:=‘ab‘‘c‘;
c里面实际存的是：ab‘c

一个是delphi字符串的引号，一个是sql拼接的作为条件的引号。

‘SELECT * FROM XXX_XX_XXXX_STATUS_CHANGE_HIST ‘+
‘WHERE RESISTNAME LIKE ‘‘‘+ComboBox1.Text+‘‘%‘‘ ‘+
‘AND BATCHNO LIKE ‘‘‘+ComboBox4.Text+‘‘%‘‘ ‘+
‘AND BOTTLENO LIKE ‘‘‘+ComboBox2.Text+‘‘%‘‘ ‘+
‘AND EQPID LIKE ‘‘‘+ComboBox3.Text+‘%‘‘ ‘+
‘AND STATUS LIKE ‘‘‘+ComboBox5.Text+‘‘%‘‘ ‘+
‘AND MODIFYTIME > ‘‘‘+(FormatDateTime(‘yyyy-mm-dd‘,DateTimePicker1.date))+‘‘‘ ‘+
‘AND MODIFYTIME <‘‘‘+(FormatDateTime(‘yyyy-mm-dd‘,DateTimePicker2.date+1))+‘‘‘ ‘+
‘ORDER BY MODIFYTIME DESC‘;

可以用Quotedstr函数

SELECT * FROM XXX_XX_XXXX_STATUS_CHANGE_HIST ‘+
‘WHERE RESISTNAME LIKE ‘+Quotedstr(ComboBox1.Text+‘%‘)
...

delphi开发环境，写SQL的查询语句，这个单引号是怎么用的，如下