The esProc table sequence is a structured two-dimensional table, having concepts of field, record, primary key and reference. These concepts originate from the data table of relational database. A table sequence is also an explicit set of genericity and orderliness, which can perform structured data computing more flex...
2015-02-03 453 0
Code reuse can make coding simpler and more efficient for program development. esProc supports basic code reuse by loop, as well as the modular programming in which a subroutine an external cellset is called. Here we’ll explain how to call a subroutine and a cross-cellset program in esProc.
1. Subroutine call
2015-02-02 464 0
During big data computing, besides data traversal and grouping and aggregate operations, sometimes we need to retrieve one group of data each time to analyze. For example, analyze sales data by dates, plot sales curve for each product, and study the purchase habit of each client.
1. Fetch data by groups according to th...
2015-01-30 426 0
esProc has some special ways to produce more orderly and more readable code, among which long statements and computational sub-statements will be illustrated in this article.
1. Long statements
If a long expression cannot be fully displayed when written in a single cell, one can write it in multiple cells according to ...
2015-01-29 528 0
esProc supports importing big data in batches with the cursor, which is the usual method used in big data computing. Usages of cursors, including external file cursor, database cursor and in-memory record sequence cursor, are basically the same. This article will take the external file cursor as the example to explain ...
2015-01-28 507 0
Table sequences are frequently used in esProc. A table sequence can be retrieved from a database, created based on data in a sequence or another table sequence using new function, or derived by using derive function to add a single or multiple columns to an existing record sequence or table sequence.
1.Create a table s...
2015-01-26 366 0
The concept of cursor is very important for the database. With the cursor, data can be manipulated more flexibly and returned from the data table by rows. esProc supports many types of cursor, like database cursor, file cursor and in-memory record sequence cursor, to satisfy various needs in data fetching and processin...
2015-01-23 506 0
Sources of data used for analysis usually fall into two categories: the database source and the file source. Compared with the database data, the file data are simple to deploy and publish. The problem is that, since the file data generally need to be used as a whole and thus need to be loaded into the memory all at on...
2015-01-20 418 0
esProc provides standard JDBC interface to be easily integrated with reporting tools. This article will explain the integration of esProc and JasperReport respectively in development environment and WEB server-side deployment.
1. Integration in development environment
Access esProc JDBC to call the esProc script using ...
It is common to sort records in the table during data analysis and computing. In esProc, sort function is used to sort data in the sequence or the table sequence. External memory sorting is required when data being sorted are massive and cannot be loaded into memory all together, for the ordinary sorting method cannot ...
2015-01-13 450 0
Besides being used to query data in a database, SQL is also used to update them. In esProc, you can use the SQL commands directly to return a query result, or use update function to modify a database with the data from a table sequence or a sequence.
1. Update a database with SQL commands
In esProc, db.execute(sql) fun...
2015-01-12 344 0
The strings in esProc sometimes include some special identifiers that may cause ambiguity about the expression. So does the names of fields in a table sequence sometimes. The following will teach you how to deal with them properly.
1. Special identifiers in strings
A string may include various signs, some of which coul...
2015-01-09 353 0
In relational databases, a foreign key is often used to identify the relationship between tables. In esProc, this relationship of correspondence can be expressed by the foreign key field.
1. Computed columns and foreign key fields
T.derive() function is used in esProc to add computed columns to a table sequence, for ex...
2015-01-08 501 0
A sequence is an ordered set consisting of some data, which are called members of the sequence. A sequence is similar to an array in high-level languages, but the data types of its members not necessarily the same. The following will explain its basic computation through creation, access, operators and functions.
2015-01-07 309 0
During our dealing with the database transactions, some operations may produce errors which could bring unexpected results, particularly during batch processes. In order to prevent this from happening, we need to manage the data connection in a right way and handle those errors properly.
1. Database error messages
2015-01-06 442 0