Resolving Incorrect Middle Dot (U+00B7) Display in SQLite CLI on Windows PowerShell

Understanding the Mismatch Between Unicode Code Points, UTF-8 Encoding, and Windows Console Rendering

Issue Overview: Misinterpretation of Middle Dot (U+00B7) in SQLite CLI on Windows PowerShell

The core issue revolves around the incorrect display of the Unicode character U+00B7 (MIDDLE DOT) when using the SQLite command-line interface (CLI) on Windows PowerShell. Users attempting to output this character observe unexpected results:

• The query SELECT '·'; truncates text after the middle dot or displays an incorrect glyph (e.g., ' instead of ·).
• The same query works correctly in Linux environments (e.g., WSL2), where the middle dot renders as expected.
• Alternative methods, such as SELECT CHAR(0xB7);, sometimes produce a different character (e.g., ・, U+30FB KATAKANA MIDDLE DOT) on Windows.

This discrepancy stems from three interrelated factors:

1. Unicode Code Point vs. UTF-8 Encoding Confusion: The user conflated the Unicode code point U+00B7 with its UTF-8 byte sequence 0xC2 0xB7, leading to incorrect assumptions about how SQLite processes the character.
2. Windows Console Limitations: The SQLite CLI on Windows converts UTF-8 to the console’s legacy code page (e.g., CP437 or CP1252) via sqlite3_win32_utf8_to_mbcs_v2(), which maps Unicode characters to glyphs available in the active code page. If the code page lacks support for U+00B7, substitution (e.g., ?) or incorrect glyphs occur.
3. Terminal Emulator Behavior: PowerShell and Windows Terminal handle UTF-8 output inconsistently compared to Linux terminals. Even with chcp 65001 (UTF-8 code page), rendering issues persist due to font limitations or terminal emulator bugs.

Root Causes: Encoding Missteps, Code Page Conflicts, and Terminal Quirks

1. Unicode Code Point vs. UTF-8 Encoding Ambiguity

• U+00B7 (MIDDLE DOT): Unicode code point 0x00B7 corresponds to the UTF-8 byte sequence 0xC2 0xB7.
• U+C2B7 Misinterpretation: The user mistakenly referenced U+C2B7 (a non-existent code point) instead of U+00B7. This confusion arises from interpreting UTF-8 bytes (C2 B7) as a hexadecimal code point (C2B7), which is invalid.
• SQLite’s Text Handling: SQLite stores and retrieves text as UTF-8, UTF-16LE, or UTF-16BE, but the CLI’s display behavior depends on terminal capabilities.

2. Windows Console Code Page and Glyph Mapping

• Legacy Code Pages: Windows defaults to code pages like CP437 (US) or CP1252 (Western European), which lack glyphs for many Unicode characters, including U+00B7. For example:
  • CP437: Maps 0xB7 to ·, but this conflicts with SQLite’s internal conversions.
  • CP1252: Includes 0xB7 as ·, but PowerShell often defaults to CP437.
• UTF-8 Code Page (65001): While chcp 65001 enables UTF-8 support, many Windows applications (including PowerShell) struggle with rendering due to:
  • Font Limitations: The active font may not include glyphs for U+00B7.
  • Buffer Bugs: Truncated output or misaligned cursors when printing multibyte UTF-8 sequences.

3. SQLite CLI’s Windows-Specific Output Handling

• Console Detection: The SQLite CLI checks if stdout is a console. If true, it converts UTF-8 to the console’s code page using WideCharToMultiByte(), which maps Unicode to the nearest equivalent in the active code page.
• Direct Output vs. Redirection: Redirecting output to a file (e.g., sqlite3.exe > output.txt) bypasses code page conversion, preserving raw UTF-8 bytes.

4. Language Settings and Fonts

• System Locale: Windows display language settings influence default code pages. For example, a Japanese locale may prioritize Shift-JIS mappings, causing CHAR(0xB7) to resolve to ・ (U+30FB) instead of ·.
• Terminal Fonts: Fonts like Consolas or MS Gothic may lack glyphs for U+00B7, leading to fallback characters.

Resolving Display Issues: Encoding Corrections, Configuration Tweaks, and Workarounds

1. Clarify Encoding Practices

• Use Unicode Code Points Explicitly:
  Instead of typing · directly (prone to encoding mismatches), use SQLite’s CHAR() function with the Unicode code point value:

  SELECT CHAR(0x00B7);  -- Unicode code point U+00B7
  

  This ensures SQLite interprets the value correctly, regardless of terminal encoding.

• Hex Literals for UTF-8 Sequences:
  For raw UTF-8 bytes, use CAST(X'...' AS TEXT):

  SELECT CAST(X'C2B7' AS TEXT);  -- UTF-8 for U+00B7
  

  This bypasses terminal input issues by directly specifying the byte sequence.

2. Configure Windows Console for UTF-8

• Enable UTF-8 Code Page:
  Run chcp 65001 in PowerShell to set the active code page to UTF-8. Combine this with:

  • Windows Terminal: Set the profile’s "Command line" to pwsh.exe -NoExit -Command "chcp 65001" to enforce UTF-8 on startup.
  • Registry Edit: Enable UTF-8 system-wide via:

    [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Nls\CodePage]
    "ACP"="65001"
    "OEMCP"="65001"
    

    Note: Reboot required. Use cautiously, as legacy apps may break.

• Font Configuration:
  In Windows Terminal, select a font with broad Unicode coverage (e.g., Cascadia Code, Noto Sans Mono).

3. Bypass Console Conversion

• Redirect Output to File:
  Capture raw UTF-8 output without console interference:

  .\sqlite3.exe "SELECT '·';" > output.txt
  

  Open output.txt in a UTF-8-aware editor (e.g., VS Code, Notepad++).

• Use PowerShell’s Pipeline:
  Decode output as UTF-8 explicitly:

  [System.Text.Encoding]::UTF8.GetString((.\sqlite3.exe "SELECT '·';" | % { [Text.Encoding]::Default.GetBytes($_) }))
  

4. Modify SQLite CLI Behavior

• Compile Custom CLI:
  Disable automatic console conversion by modifying shell.c in SQLite’s source:

  // Comment out or remove calls to sqlite3_win32_utf8_to_mbcs_v2()
  // in the console output logic.
  

  Recompile to emit raw UTF-8 regardless of output destination.

• Use WSL or Linux Subsystems:
  Run SQLite in WSL2, where UTF-8 handling is consistent with Linux.

5. Validate Environment Settings

• Check Active Code Page:
  Verify with chcp in PowerShell. If not 65001, revisit configuration steps.
• Test Glyph Availability:
  Use PowerShell to test if U+00B7 renders correctly:

  [System.Char]::ConvertFromUtf32(0x00B7)
  

  If this displays ·, the issue lies with SQLite CLI’s conversion. If not, adjust fonts or code pages.

6. Alternative Middle Dot Representations

• HTML Entities in Queries:
  For web applications, use '·' and process externally. Not applicable to CLI.
• ASCII Substitutes:
  Temporarily use * or - if the middle dot is purely decorative.

Final Notes:
The root cause is not SQLite itself but the interplay between Windows console limitations, encoding settings, and font support. By aligning terminal configurations with UTF-8 standards and using explicit encoding methods in queries, users can reliably display U+00B7 and other Unicode characters. For mission-critical applications, consider redirecting output to files or using subsystems with robust UTF-8 support.