Scalar Functions — String

String scalar functions cover manipulation, searching, encoding, parsing, and formatting of text values. ClickHouse and DuckDB have the broadest support. Several functions — including split(), replace_regex(), extract(), and all encoding functions — are unavailable in SQLite.

Legend: ✅ Supported · ⚠️ Approximated · ❌ Not Supported · 🔄 Rewritten

Function	SQLite	MySQL	ClickHouse	PostgreSQL	DuckDB	Notes
`strlen()`	✅	✅	✅	✅	✅	`length()`
`toupper()`	✅	✅	✅	✅	✅	`upper()`
`tolower()`	✅	✅	✅	✅	✅	`lower()`
`substring()`	✅	✅	✅	✅	✅	`substr()`; ClickHouse index offset corrected; DuckDB 0-based (no offset)
`indexof()`	✅	✅	✅	✅	✅	0-based; occurrence arg not supported with warning
`strcat()`	✅	✅	✅	✅	✅	SQLite/Postgres/DuckDB: `\|\|`; MySQL: `concat()` with NULL warning
`strcat_delim()`	✅	✅	✅	✅	✅	`concat_ws()`
`strcat_array()`	❌	❌	✅	✅	✅	Postgres/DuckDB: `array_to_string`; ClickHouse: `arrayStringConcat`
`split()`	❌	❌	✅	✅	✅	Postgres: `string_to_array`; DuckDB: `string_split`; ClickHouse: `splitByString`
`replace_string()`	✅	✅	✅	✅	✅	`replace()`
`replace_regex()`	❌	✅	✅	✅	✅	SQLite: unsupported
`reverse()`	❌	✅	✅	✅	✅	SQLite: unsupported (no built-in reversal)
`trim()`	✅	✅	✅	✅	✅	With regex arg: ClickHouse/Postgres/MySQL/DuckDB only (not SQLite)
`trim_start()`	✅	✅	✅	✅	✅	`ltrim()` / `trimLeft()`
`trim_end()`	✅	✅	✅	✅	✅	`rtrim()` / `trimRight()`
`isempty()`	✅	✅	✅	✅	✅	ClickHouse: `isNull OR empty`
`isnotempty()`	✅	✅	✅	✅	✅
`isnull()`	✅	✅	✅	✅	✅	`IS NULL`
`isnotnull()`	✅	✅	✅	✅	✅	`IS NOT NULL`
`countof()`	❌	❌	✅	⚠️	⚠️	ClickHouse: `countSubstrings()`; Postgres/DuckDB: length-delta count — counts non-overlapping matches only (KQL counts overlapping), ignores the `kind` argument, and an empty needle errors
`strrep()`	❌	✅	✅	✅	✅	`repeat()`
`strcmp()`	✅	✅	✅	✅	✅	CASE-based −1/0/1
`extract()`	❌	✅	✅	✅	✅	SQLite: unsupported; DuckDB: `regexp_extract`
`extract_all()`	❌	❌	✅	❌	✅	ClickHouse: `extractAll()`; DuckDB: `regexp_extract_all()`
`translate()`	❌	❌	✅	✅	✅
`url_encode()`	❌	❌	✅	❌	✅	ClickHouse: `encodeURLComponent`; DuckDB: `url_encode`
`url_decode()`	❌	❌	✅	❌	✅	ClickHouse: `decodeURLComponent`; DuckDB: `url_decode`
`base64_encode_tostring()`	❌	❌	✅	❌	✅	ClickHouse: `base64Encode`; DuckDB: `base64()` (BLOB cast)
`base64_decode_tostring()`	❌	❌	✅	❌	✅	ClickHouse: `base64Decode`; DuckDB: `from_base64`
`parse_json()`	❌	✅	✅	✅	✅
`parse_url()`	❌	❌	✅	❌	✅	DuckDB: regex-based; Scheme/Host/Port/Path/Query/Fragment only
`parse_urlquery()`	❌	❌	✅	❌	✅
`normalize_path()`	❌	⚠️	⚠️	⚠️	⚠️	ClickHouse: `replaceAll` + `replaceRegexpAll`; Postgres/DuckDB: `replace` + `regexp_replace`; MySQL: `REPLACE` + `REGEXP_REPLACE`; all with warning