Blank Lines Between Rows in SQLite CLI Due to Hidden Newline Characters

Diagnosing Unexpected Line Breaks in SQLite CLI Column Output

Understanding the Core Display Anomaly

The issue at hand involves unexpected blank lines appearing between rows when querying a specific column (e.g., status) in SQLite’s command-line interface (CLI). These gaps are not present in the underlying data but manifest during result rendering. Key observations include:

1. Blank lines occur only when querying a single column containing values with embedded newline characters.
2. Multi-column queries do not exhibit the same behavior, even if one column contains newlines.
3. The anomaly persists across macOS environments with SQLite 3.44.2 and specific CLI configuration flags.

This phenomenon arises from the interaction between SQLite’s output formatting logic and non-printable control characters within column values. When a cell contains a line break (\n or \r), the CLI’s column display mode splits the cell content across multiple terminal lines. However, the row separator (default: \n) is applied after the entire logical row, including all cell lines. This creates visual gaps between subsequent rows when a preceding row’s cell spans multiple lines.

For example, a status value like 'sect.\n nov.' will occupy two terminal lines. The row separator adds a newline after the second line, causing the next row to start two lines below the prior row’s first line. This creates the illusion of a blank line between rows.

Root Causes: Data Structure and CLI Configuration Synergy

Three interrelated factors contribute to this behavior:

1. Embedded Newline Characters in Column Values
The primary trigger is the presence of unescaped newline characters (CHAR(10)) within stored data. These often originate from:

• Accidental pasting of multi-line text into INSERT/UPDATE statements.
• Improper sanitization of imported data (e.g., CSV files with unquoted line breaks).
• Application code that permits free-form text input without escaping.

2. Column Mode Rendering Logic
SQLite CLI’s column mode (enabled via .mode column) formats output into aligned columns. When a cell’s content exceeds the column width or contains newlines, the CLI:

• Splits the content into multiple lines within the same logical row.
• Prints all lines of the current row before moving to the next row.
• Applies the rowseparator (default: \n) once per logical row, not per cell line.

This causes multi-line cells to visually "push down" subsequent rows, leaving blank spaces where users expect contiguous rows.

3. Configuration Settings Amplifying the Effect
The user’s specific CLI settings exacerbate the issue:

• .mode column --wrap 60 --wordwrap off --noquote: Disables text wrapping and quoting, forcing raw display of newlines.
• colseparator: "|" and rowseparator: "\n": Uses minimal separators, lacking visual cues to distinguish cell lines from row separators.
• headers: on: Adds a header row, which may misalign with data rows if the first data row has multi-line cells.

Resolving the Issue: Data Cleansing and Output Adjustments

Step 1: Identify Rows with Embedded Newlines
Execute a query to locate problematic values:

SELECT rowid, status 
FROM treatments 
WHERE status LIKE '%' || CHAR(10) || '%' 
   OR status LIKE '%' || CHAR(13) || '%';

Replace CHAR(10)/CHAR(13) with hex literals if necessary:

WHERE INSTR(status, X'0A') > 0 
   OR INSTR(status, X'0D') > 0;

Step 2: Sanitize Existing Data
Remove or replace newlines using UPDATE:

UPDATE treatments 
SET status = REPLACE(REPLACE(status, CHAR(10), ' '), CHAR(13), '') 
WHERE INSTR(status, CHAR(10)) > 0 
   OR INSTR(status, CHAR(13)) > 0;

For selective replacement (e.g., preserve intentional line breaks), use a regex-based approach with the REGEXP extension.

Step 3: Adjust CLI Output Settings
Modify formatting to minimize ambiguity:
A. Enable quoting to encapsulate cells with newlines:

.mode quote

B. Switch to list mode with a visible row separator:

.mode list
.separator "|" "\n"

C. Force single-line display by suppressing wrapping:

.mode column --wrap 0

Step 4: Prevent Future Occurrences
Add constraints or triggers to reject/clean values with newlines:

CREATE TRIGGER trg_treatments_status_no_newlines 
BEFORE INSERT ON treatments 
BEGIN 
  SELECT RAISE(ABORT, 'status contains newline')
  WHERE INSTR(NEW.status, CHAR(10)) > 0 
     OR INSTR(NEW.status, CHAR(13)) > 0;
END;

Step 5: Utilize Alternative Output Formats
For scripting or automated processing, bypass CLI formatting entirely:

sqlite3 -csv db.sqlite "SELECT status FROM treatments" 

By systematically addressing both the data anomalies and the CLI’s rendering behavior, users can eliminate unintended blank lines while maintaining readability and data integrity.