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In SQL, the unique keys have a UNIQUE constraint assigned to them in order to prevent duplicates (a duplicate entry is not valid in a unique column). Alternate keys may be used like the primary key when doing a single-table select or when filtering in a where clause, but are not typically used to join multiple tables.
dplyr is an R package whose set of functions are designed to enable dataframe (a spreadsheet-like data structure) manipulation in an intuitive, user-friendly way. It is one of the core packages of the popular tidyverse set of packages in the R programming language . [ 1 ]
A database index is a data structure that improves the speed of data retrieval operations on a database table at the cost of additional writes and storage space to maintain the index data structure. Indexes are used to quickly locate data without having to search every row in a database table every time said table is accessed.
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Previous Page: sort the data in the reverse order, select only the first {rows} rows, where the {unique_key} is less than {first_val} (the value of the {unique_key} of the first row in the current page), and sort the result in the correct order; Read and send to display all the rows read from the database
A database table can be thought of as consisting of rows and columns. [1] Each row in a table represents a set of related data, and every row in the table has the same structure. For example, in a table that represents companies, each row might represent a single company. Columns might represent things like company name, address, etc.
In MySQL, UTF-8 is called utf8mb4, [79] while utf8 and utf8mb3 refer to the obsolete CESU-8 variant. [80] In Oracle Database (since version 9.0), AL32UTF8 [81] means UTF-8, while UTF-8 means CESU-8. In HP PCL, the Symbol-ID for UTF-8 is 18N. [82] There are several current definitions of UTF-8 in various standards documents:
Being described as the Aadhaar for land, Unique Land Parcel Identification Number (ULPIN) is a 14-digits alphanumeric unique ID for each and every land parcel in India. [citation needed] Ultimately ULPIN will be used as single source of truth for land records in near future as it is designed to uniquely identify every surveyed land parcel in india based on the Textual records of rights (RoR ...