LIKE Patterns

Percent Prefix

A trailing percent sign allows extra following text.

highlighted = computed this step

Percent wildcard at the end

A percent sign can stand for any remaining characters.

prefix then percent\text{prefix then percent}

Read prefix matches

The pattern keeps 2 rows that start with Al.

TRUE rows=2\text{TRUE rows}=2

LIKE-pattern examples are tiny finite WHERE-style filters with a small SQL-like pattern subset; collations, escapes, dialect behavior, indexes, optimizer behavior, and product claims are out of scope.

Percent wildcard at the end: base rowsidname1Ada2Al3Alan4Bea5Jo6NULL LIKE evaluationsourcevaluepatterntruthkept0AdaAl%FALSEno1AlAl%TRUEyes2AlanAl%TRUEyes3BeaAl%FALSEno4JoAl%FALSEno5NULLAl%UNKNOWNno LIKE output rowsidname2Al3Alan LIKE factsfactvalueinputRowCount6outputRowCount2trueRows2falseRows3unknownRows1patternKindpercentrowOrdersource_order

Short or longer

Al matches, and Alan also matches because percent can cover the rest.

rest may be empty or longer\text{rest may be empty or longer}

Summary

Text before percent is a required prefix in this tiny model.

required prefix\text{required prefix}