Awk is a POSIX-standard command line tool and programming language for processing DSV data. If you use Linux, macOS or a BSD, you almost certainly have it installed. See below for Windows.
If you already know how to program, the nawk man page is a great way to learn Awk quickly. What you learn from it will apply to other implementations on different platforms. Read it first if you feel overwhelmed by the sheer size of the GNU Awk manual.
A multitool. Compare, filter, normalize, split, and validate CSV files. Reorder, remove, split, and merge fields. Convert data between fixed-width, multi-line, XML, and DSV format. Generate SQL statements. Documentation.
Search, sample, cut, join, transpose, and sort CSV/TSV files. Rename columns. Replace fields and generate new fiends from existing fields. Plot data as vector or raster histograms and box, line, and scatter plots. Convert CSV to Markdown. Convert XLSX to CSV. Split XLSX sheets.
A Python library with a CLI. Convert between a number of file formats for tabular data: CSV, XLS, XLSX, ODS, and others. Query the data (via SQLite). Combine tables. Generate schemas.
A number of simple utilities (like hxcopy, hxpipe, hxunent, hxselect) for manipulating HTML and XML files from W3C. Written in C, quite old-fashioned, but still relevant and maintained.
Create and manipulate JSON with a DSL inspired by Rust, C and JavaScript. Similar to jq. Supports JSON, YAML and TOML as well as binary formats like Apache Avro and MessagePack.
Retrieve properties and sections as shell script commands to set the corresponding variables. Retrieve properties' values as plain text. Check for existence of properties. List sections. Find values that match a pattern. Read-only.
Retrieve properties and sections as INI fragments or shell script commands to set the corresponding variables. Retrieve properties' values as plain text. Set properties. Remove properties and sections. Create empty sections. Merge INI files. Changes files in place.
Retrieve properties and sections as batch file commands to set the corresponding variables. Set properties. Remove properties and sections. Changes files in place.
Retrieve properties and sections as INI fragments. Retrieve properties' values as plain text. Set properties. Check for existence of properties and sections. Remove properties and sections. Outputs the updated INI file.
Query and watch log files. Has batch and interactive mode. Supported formats include the Common Log Format, CUPS page_log, syslog, strace, and generic timestamped messages. Can perform SQL queries.
Query and modify a number of file formats. Not all of the formats are equally well supported by Augeas and for some only a limited subset of all valid files can be parsed.
Query and modify configuration files. Shares Augeas' limitations when it comes to application-specific configuration files (it uses the same lenses), but has better support for generic formats such as JSON and INI.
Firebird is a FOSS database that can be used from a single file, like SQLite. "isql is a program that allows the user to issue arbitrary SQL commands".