You can also specify descending order: posts. If you would like to add to the existing order, use order_append or order_prepend: posts. Order always overrides the existing order: posts. Ordering datasets is simple using order: posts. # SELECT avg(price) FROM items Ordering Records ¶ ↑ Or calculate a sum or average via sum and avg: sum = DB. # SELECT max(value) FROM history min = DB. count # SELECT COUNT(*) FROM posts WHERE (category LIKE '%ruby%' ESCAPE '\')Īnd you can also query maximum/minimum values via max and min: max = DB. Summarizing Records ¶ ↑Ĭounting records is easy using count: posts. Please read the Security Guide for details on security issues that you should be aware of when using Sequel. Security ¶ ↑ĭesigning apps with security in mind is a best practice. See the Dataset Filtering file for more details. # Print out the number of records puts "Item count: # create_table :items do primary_key :id String :name Float :price end items = DB # Create a dataset # Populate the table items. (If the DBA will permit that - many/most wont). Modify the FK on the child table(s) TO 'ON DELETE CASCADE'. Set this but do NOT actually delete the user. sqlite # memory database, requires sqlite3 DB. Add a column to users table indicating that 'user has been deleted'. Installation ¶ ↑ gem install sequel A Short Example ¶ ↑ require 'sequel' DB = Sequel. If you have any comments or suggestions please post to the Google group. To check out the source code: git clone git:///jeremyevans/sequel.git Contact ¶ ↑ Only use the the bug tracker to report bugs in Sequel, not to ask for help on using Sequel. If you have questions about how to use Sequel, please ask on GitHub Discussions or the sequel-talk Google Group. jeremyevans/sequel/discussions Alternate Discussion Forum (sequel-talk Google Group) jeremyevans/sequel/issues Discussion Forum (GitHub Discussions) jeremyevans/sequel Bug tracking (GitHub Issues) Sequel currently has adapters for ADO, Amalgalite, IBM_DB, JDBC, MySQL, Mysql2, ODBC, Oracle, PostgreSQL, SQLAnywhere, SQLite3, TinyTDS, and Trilogy. Sequel supports advanced database features such as prepared statements, bound variables, savepoints, two-phase commit, transaction isolation, primary/replica configurations, and database sharding. Sequel includes a comprehensive ORM layer for mapping records to Ruby objects and handling associated records. Sequel provides thread safety, connection pooling and a concise DSL for constructing SQL queries and table schemas. Table.AlternateRows ( Previous Step, 0 first row, 1 only remove one row, Table. Sequel is a simple, flexible, and powerful SQL database access toolkit for Ruby. This will delete the first row ( power query is index 0) Table.AlternateRows (Source,0,1,Table.RowCount (Source)) And here is my understanding of how it works. There can be many rows that fulfill the condition, it can be just one row, or no rows at all.Sequel: The Database Toolkit for Ruby ¶ ↑ You can write the condition for which the rows should be removed. Sometimes, you don't know the exact rows you need to remove or even how many rows you need to remove. You want to remove all rows for which the result is greater than 10. In the exam table, there are names of the students and the results of the exam, just as in the previous example. If there is no such name, no rows are removed. However, after saving the file, closing it. I then proceeded to clear the formatting from all of the unused rows, and then - just in case - selected all the blank rows (beneath my data) using alt Shift and alt Shift , then right-click and delete. If there are many rows whose name equals ' Ellen Thornton', all of them will be removed. Oddly enough, that cell was in the last possible row in the sheet (i.e. If you have a specific row in mind, it is best to write the condition using the column containing unique values. In WHERE, write the condition specifying the row. Use DELETE FROM with the name of the table from which you'd like to delete a row. You want to remove the row for Ellen Thornton. In the exam table, there are names of the students and the results of the exam. You want to remove a row / rows from a table.
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