SELECT
PDBC_PFX, BSBS_TYPE,
STRING_AGG(CAST(BSTX_TEXT AS VARCHAR(MAX)), '') WITHIN GROUP ( ORDER BY BSTX_SEQ_NO ASC ) AS BSTX0
FROM dbo.CMC_BSTX_SUM_TEXT
WHERE PDBC_PFX = 'EH38' AND BSBS_TYPE = 'SOBD'
GROUP BY PDBC_PFX, BSBS_TYPE