是否可以在cql脚本的cql命令中使用变量？

问题描述

在CQL脚本中使用时，是否可以通过CQL命令传递变量？

Is there a way to pass variables in CQL commands when being used in CQL scripts like:

select * from "Column Family Name" where "ColumnName"='A variable which takes different values';

欢迎提出任何建议。

推荐答案

不，CQL确实没有定义变量，运行循环以及基于这些变量进行更新/查询的方法。

No, CQL really doesn't have a way to define variables, run a loop, and update/query based on those variables.

作为替代，我通常将用于这样的简单任务/脚本。这是我使用一段时间后从CSV文件填充产品颜色的Python脚本的摘录。

As an alternative, I typically use the DataStax Python driver for simple tasks/scripts like this. Here is an excerpt from a Python script I used a while back to populate product colors from a CSV file.

# connect to Cassandra
auth_provider = PlainTextAuthProvider(username='username', password='currentHorseBatteryStaple')
cluster = Cluster(['127.0.0.1'], auth_provider=auth_provider)
session = cluster.connect('products')

# prepare statements
preparedUpdate = session.prepare(
    """
        UPDATE products.productsByItemID SET color=? WHERE itemid=? AND productid=?;
    """
)
# end prepare statements

counter = 0

# read csv file
dataFile = csv.DictReader(csvfilename, delimiter=',')
for csvRow in dataFile:
    itemid = csvRow['itemid']
    color = csvRow['customcolor']
    productid = csvRow['productid']

    #update product color
    session.execute(preparedUpdate,[color,itemid,productid])

    counter = counter + 1

# close Cassandra connection
session.cluster.shutdown()
session.shutdown()

print "updated %d colors" % (counter)

有关更多信息，请参见DataStax教程。

For more information, check the DataStax tutorial Getting Started with Apache Cassandra and Python.

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