
该LIKE条件允许我们在SQL语句的where子句中使用通配符.这允许我们执行模式匹配.该LIKE条件可用于任何有效的SQL语句 - 选择,插入,更新或删除.像这样
SELECT * FROM users
WHERE user_name like 'babu%';
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与上面相同的操作一样,任何查询都可以在CLI中用于Cassandra.
我在我的java程序中使用iText来编辑现有的pdf.生成的pdf无法打开,它显示pdf header signature not found error.I我同时使用我的输入和输出文件.
private static String INPUTFILE = "/sample.pdf";
private static String OUTPUTFILE = "/sample.pdf";
public static void main(String[] args)
throws DocumentException,
IOException
{
Document doc = new Document();
PdfWriter writer = PdfWriter.getInstance(doc,new FileOutputStream(OUTPUTFILE));
doc.open();
PdfReader reader = new PdfReader(INPUTFILE);
int n;
n = reader.getNumberOfPages();
System.out.println("No. of Pages :" +n);
for (int i = 1; i <= n; i++)
{
if (i == 1)
{
Rectangle rect = new Rectangle(85,650,800,833);
PdfFormField pushbutton = PdfFormField.createPushButton(writer);
pushbutton.setWidget(rect, PdfAnnotation.HIGHLIGHT_PUSH);
PdfContentByte …Run Code Online (Sandbox Code Playgroud) 在下面的cassandra中,"获取结果"..我们可以检索列名和值.但是如何检索时间戳..是否有更好的想法通过使用时间戳来获取值
[default@sample]get user[bob];
=> (column=name, value=bobdroid, timestamp=1335361733545850)
=> (column=email, value=bob@gmail.com, timestamp=1335361733545850)
=> (column=age, value=23, timestamp=1335361733545850)
=> (column=password, value=MTIz, timestamp=1335361733545850)
Returned 4 results.
Elapsed time: 4 msec(s).
Run Code Online (Sandbox Code Playgroud) 这是我的Django模型
class author(models.Model):
name = models.CharField('name',max_length=140)
datamode = models.CharField(max_length=1, default='A', choices=DATAMODE_CHOICE)
def __str__(self):
return '%s' % (self.name)
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虽然我author在另一个类中使用此类作为外键,如下所示:
class books(models.Model):
NEW_FLAG=(('N','New'),('O','Old'))
name = models.CharField('name',max_length=140)
author = models.ForeignKey(author, blank=True, null=True)
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当我在管理员中输入新书详细信息时,它显示:
IntegrityError: Column 'author_id' cannot be null.
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