Blockchain systems rely on consensus mechanisms to ensure data consistency among nodes. However, this also confines the trust boundary of data to a single chain, resulting in inherent “data silos” across distinct blockchain systems. In practical applications, data across different blockchains often exhibit correlations. Unsynchronized operations on independent chains can easily disrupt these correlations, threatening inter-chain data consistency. Cross-chain technology is a key solution for breaking down these silos, enabling blockchain interoperability, and enhancing system scalability. Cross-chain transactions, which serve as the core mechanism for maintaining global consistency in cross-chain systems, provide the fundamental underpinning for building a scalable, interoperable ecosystem. Existing surveys on cross-chain technologies predominantly focus on cross-chain atomicity, while providing less comprehensive discussions of cross-chain transaction technologies. Through a systematic review of the relevant literature, this study (1) clarifies the concept of cross-chain system consistency constraints and defines cross-chain transactions; (2) analyzes the key technical challenges faced by cross-chain transactions, reviews the current state of research, and conducts a multidimensional comparative analysis; (3) evaluates representative holistic solutions from the perspective of key technologies and identifies several future research directions worthy of in-depth exploration.