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String Functions

What is it?

CDS provides a set of built-in string functions for concatenation, trimming, padding, case conversion, searching, and substring extraction — evaluated directly in the database.

Why is it used?

To manipulate text fields (formatting, combining, searching) without transferring rows to the application server first.

When should it be used?

Use CDS string functions whenever the transformation can be expressed declaratively in the view — reserve ABAP-side string handling for logic that's genuinely program-specific or too complex for SQL.

Examples (original notes, with output annotated)

// String Functions in CDS
// Assume: Text1 = 'Example'  (7 characters)
//         Text2 = 'Sample'   (6 characters)

// Concat: Concatenate Strings
concat(Text1, Text2)               // => ExampleSample

// Concat w/ Separator: Add Separator Between Strings
concat(concat(Text1, ','), Text2)  // => Example,Sample

// Concat w/ Space: Add Space Between Strings
concat_with_space(Text1, Text2, 1) // => Example Sample     | 1 Character Space
concat_with_space(Text1, Text2, 3) // => Example   Sample   | 3 Character Space

// Left & Right: Get Left & Right Part of String
left(Text1, 2)   // => Ex
right(Text1, 2)  // => le

// Left & Right: Ex
left outer join /sapsll/maritc as Maritc on Maritc.matnr           = _Item.matnr
                                        and left(Maritc.ccngn, 17) = I_ProductPlant.Commodity

// Lpad & Rpad: Pad to a Total Length With a Character
lpad(Text1, 10, '0') // => 000Example  | padded from 7 to 10 characters
rpad(Text2, 10, '0') // => Sample0000  | padded from 6 to 10 characters

// Lowercase & Uppercase: Convert to Lower & Upper
lowercase(Text2) // => sample
uppercase(Text1) // => EXAMPLE

// Instr: Find Position of Character
instr(Text1, 'a')   // => 3
instr(Text1, 'z')   // => 0
instr(Text2, 'mp')  // => 3

// Length: Find Length of String
length(Text1) // => 7

// Ltrim & Rtrim: Delete Left & Right Matched Character
ltrim(Text1, 'E') // => xample
rtrim(Text2, 'e') // => Sampl

// Replace: Replace Character in String
replace(Text1, 'a', 'o')                 // => Exomple
replace(Text1, 'Example', 'SampleText')  // => SampleText

// Substring: Get Substring of String
substring(Text1, 2, 3) // => xam

📝 concat() takes exactly two arguments. The original note wrote the separator example as concat(concat(Text1, ',', Text2)) — an inner call with three arguments, which does not compile. The corrected form above nests the calls: concat(concat(Text1, ','), Text2), i.e. first append the separator to Text1, then append Text2 to that result. Unlike ABAP's CONCATENATE ... SEPARATED BY, CDS concat() is strictly binary and must be nested for more than two parts; use concat_with_space when the separator is a space.

Function Reference

Function Signature Purpose
concat(a, b) 2 args Concatenates two strings.
concat_with_space(a, b, n) 3 args Concatenates a and b with n spaces in between.
left(str, n) / right(str, n) First/last n characters.
lpad(str, len, char) / rpad(str, len, char) Pads str on the left/right with char until it reaches len characters.
lowercase(str) / uppercase(str) Case conversion.
instr(str, substr) 1-based position of the first occurrence of substr in str; 0 if not found.
length(str) Character length of str.
ltrim(str, char) / rtrim(str, char) Removes leading/trailing occurrences of char.
replace(str, from, to) Replaces all occurrences of from with to.
substring(str, pos, len) Extracts len characters starting at 1-based position pos.

Real Business Example — Building a Commodity Code Match

left outer join /sapsll/maritc as Maritc
  on  Maritc.matnr           = _Item.matnr
  and left(Maritc.ccngn, 17) = I_ProductPlant.Commodity

Here left() truncates a longer commodity code (ccngn) down to the first 17 characters so it can be compared against a shorter commodity code field — a real pattern from foreign trade / GTS integration, where code lengths differ between systems.

Common Mistakes

  • ❌ Assuming concat() accepts more than two arguments (see the note above) — nest calls or use concat_with_space instead.
  • ❌ Using instr() and treating a 0 result as "found at the start" — 0 means not found; CDS string positions are 1-based.
  • ❌ Chaining many string functions in the field list instead of considering whether a cleaner data model (e.g. a real join key) would avoid needing string manipulation at all.

Performance Considerations

  • String functions execute per row in the database — generally cheap, but heavy use of replace/instr on very wide tables can still add up; check ST05 if a view feels unexpectedly slow.
  • Prefer left(str, n) over substring(str, 1, n) when extracting from the start — functionally equivalent, but left/right communicate intent more clearly.

SAP Best Practices

  • Use string functions for presentation/matching logic, not as a substitute for properly normalized keys.
  • Favor concat_with_space over manual concat(concat(a, ' '), b) chains when a literal space separator is all that's needed — it's shorter and clearer.
  • Remember lpad/rpad take a total target length, not a number of padding characters — lpad('Example', 10, '0') yields 000Example, not ten zeros followed by the text.

Interview Notes

  • Q: How many arguments does concat() take in CDS? A: Exactly two — for more parts, nest additional concat() calls.
  • Q: What does instr() return when the substring is not found? A: 0.

Related Chapters

  • Math.md — numeric built-in functions
  • Conversion.md — cast() and type conversion, often paired with string functions